Rotor, stator and motor

ABSTRACT

A rotor with four axially stacked rotor cores, and a plurality of field magnets interposed between them. Each rotor core includes a rotor-side claw-shaped magnetic pole. Each rotor-side claw-shaped magnetic poles are respectively extending from and formed on each rotor core at equal angle intervals. Tip end surfaces of the first and third rotor-side claw-shaped magnetic pole abut against or are closely opposed to each other axially. Tip end surfaces of the second and fourth rotor-side claw-shaped magnetic poles abut against or are closely opposed to each other in the axial direction. The plurality of field magnets are magnetized in the axial direction such that the field magnets causes the first and third rotor-side claw-shaped magnetic poles to function as first magnetic poles, and cause the second and fourth rotor-side claw-shaped magnetic poles to function as second magnetic poles.

BACKGROUND OF THE INVENTION

The present invention relates to a rotor, a stator and a motor.

A rotor of a so-called Lundell type structure is a known rotor used fora motor. The rotor of the Lundell type structure has a pair of rotorcores and a field magnet placed between the pair of rotor cores in anaxial direction of the rotor. Each of the rotor cores includes adisk-shaped core base and a plurality of claw-shaped magnetic polesarranged on an outer periphery of the core base. The pair of rotor coresare combined with each other such that the claw-shaped magnetic polesare alternately arranged in a circumferential direction of the rotor.The claw-shaped magnetic poles alternately function as north poles andsouth poles. For example, a rotor of a Lundell type structure disclosedin Japanese Laid-Open Utility Model Publication No. 5-43749 is of atwo-part structure using two sets of rotor structures each including apair of rotor cores and a field magnet.

The rotor of the Lundell type structure has room for improvement interms of higher output and assembling properties.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a rotor, a statorand a motor capable of improving their outputs and assemblingproperties.

To achieve the above objectives, according to first aspect of thepresent invention, a rotor includes first to fourth four rotor coresstacked on one another in order in an axial direction of the rotor, anda plurality of field magnets respectively interposed between the firstto fourth rotor cores. The first to fourth rotor cores respectivelyinclude same number of first to fourth rotor-side claw-shaped magneticpoles The first to fourth rotor-side claw-shaped magnetic poles arerespectively extending from and formed on the first to fourth rotorcores at equal angle intervals. A tip end surface of the firstrotor-side claw-shaped magnetic pole and a tip end surface of the thirdrotor-side claw-shaped magnetic pole abut against or are closely opposedto each other in the axial direction. A tip end surface of the secondrotor-side claw-shaped magnetic pole and a tip end surface of the fourthrotor-side claw-shaped magnetic pole abut against or are closely opposedto each other in the axial direction. The plurality of field magnets aremagnetized in the axial direction such that the field magnets cause thefirst and third rotor-side claw-shaped magnetic poles to function asfirst magnetic poles, and cause the second and fourth rotor-sideclaw-shaped magnetic poles to function as second magnetic poles.

According to second aspect of the present invention, a stator includesfirst to fourth four stator cores stacked on one another in order in anaxial direction of the stator, and a plurality of annular windingsrespectively interposed between the first to fourth stator cores. Thefirst to fourth stator cores respectively include same number of firstto fourth stator-side claw-shaped magnetic poles. The first to fourthstator-side claw-shaped magnetic poles are respectively extending fromand formed on the first to fourth stator cores at equal angle intervals.A tip end surface of the first stator-side claw-shaped magnetic pole anda tip end surface of the third stator-side claw-shaped magnetic poleabut against or are closely opposed to each other in the axialdirection. A tip end surface of the second stator-side claw-shapedmagnetic pole and a tip end surface of the fourth stator-sideclaw-shaped magnetic pole abut against or are closely opposed to eachother in the axial direction. Directions of AC current flowing throughthe plurality of annular windings are different from one another suchthat a variation cycle of magnetic fluxes from the first and thirdstator-side claw-shaped magnetic poles and a variation cycle of magneticfluxes from the second and fourth stator-side claw-shaped magnetic polesare deviated from each other in phase by 180°.

According to third aspect of the present invention, a motor includes ashaft extending along an axial direction of the motor; a rotor; and astator. The rotor includes a first rotor core having a plurality offirst rotor claw-shaped magnetic poles arranged at equal intervals fromone another in a circumferential direction of the motor, a second rotorcore having a plurality of second rotor claw-shaped magnetic polesarranged at equal intervals from one another in the circumferentialdirection, and an annular field magnet placed between the first andsecond rotor cores and magnetized in the axial direction. The first andsecond rotor claw-shaped magnetic poles are alternately placed in thecircumferential direction. The field magnet is configured so as to causethe first and second rotor claw-shaped magnetic poles to function asmagnetic poles which are different from each other. The stator includesa first stator core having a plurality of first stator claw-shapedmagnetic poles arranged at equal intervals from one another in thecircumferential direction, a second stator core having a plurality ofsecond stator claw-shaped magnetic poles arranged at equal intervalsfrom one another in the circumferential direction, and a coil portionplaced between the first and second stator cores and wound in thecircumferential direction. The first and second stator claw-shapedmagnetic poles are placed alternately in the circumferential directionand are opposed to the first and second rotor claw-shaped magneticpoles. The coil portion is configured so as to cause the first andsecond stator claw-shaped magnetic poles to function as magnetic poleswhich are different from each other based on energization to the coilportion, and cause polarities of the first and second stator claw-shapedmagnetic poles to switch to each other. The shaft extends through one ofthe rotor and the stator. The first and second rotor and the first andsecond stator have an equal number of claw-shaped magnetic poles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a perspective view of a brushless motor according to a firstembodiment of the present invention;

FIG. 2 is a sectional view of the brushless motor shown in FIG. 1;

FIG. 3 is a perspective view of a single motor shown in FIG. 1;

FIG. 4 is a front view of the single motor shown in FIG. 3 as viewedfrom its axial direction;

FIG. 5A is a combined sectional view of a single rotor shown in FIG. 4taken along line A-O-A;

FIG. 5B is a combined sectional view of a single stator shown in FIG. 4taken along line A-O-A;

FIG. 6 is an exploded perspective view of the single motor shown in FIG.3;

FIG. 7 is an exploded perspective view of the single rotor shown in FIG.3;

FIG. 8 is an exploded perspective view of the single stator shown inFIG. 3;

FIG. 9 is a perspective view of an entire three-phase rotor shown inFIG. 1;

FIG. 10 is a front view of the three-phase rotor shown in FIG. 9 asviewed from its radial direction of the rotor;

FIG. 11 is a sectional view of the three-phase rotor shown in FIG. 9;

FIG. 12 is a perspective view of an entire three-phase stator shown inFIG. 9;

FIG. 13 is a sectional view of the three-phase stator shown in FIG. 9;

FIG. 14 is a waveform diagram of each of phases of a three-phase ACpower source shown in FIG. 9;

FIG. 15 is an exploded perspective view of a single motor configuring abrushless motor according to a second embodiment of the presentinvention;

FIG. 16A is a sectional view of a single rotor shown in FIG. 15;

FIG. 16B is a sectional view of a single stator shown in FIG. 15;

FIG. 17 is a perspective view of an entire three-phase rotor;

FIG. 18 is a front view of the three-phase rotor shown in FIG. 17 asviewed from its radial direction;

FIG. 19 is a perspective view of an entire three-phase stator;

FIG. 20 is a sectional view of the three-phase stator;

FIG. 21 is a diagram of torque characteristics showing comparisonbetween current and torque;

FIG. 22 is an exploded perspective view of a single motor configuring abrushless motor according to a third embodiment of the presentinvention;

FIG. 23A is a sectional view of a single rotor shown in FIG. 22;

FIG. 23B is a sectional view of a single stator shown in FIG. 22;

FIG. 24 is a perspective view of an entire three-phase rotor;

FIG. 25 is a front view of the three-phase rotor shown in FIG. 24 asviewed from its radial direction;

FIG. 26 is a perspective view of an entire three-phase stator;

FIG. 27 is a sectional view of the three-phase stator shown in FIG. 26;

FIG. 28 is a diagram of torque characteristics showing comparisonbetween current and torque;

FIG. 29 is an exploded perspective view of a single motor configuring abrushless motor according to a fourth embodiment of the presentinvention;

FIG. 30A is a sectional view of a single rotor shown in FIG. 29;

FIG. 30B is a sectional view of a single stator shown in FIG. 29;

FIG. 31 is a perspective view of an entire three-phase rotor;

FIG. 32 is a front view of the three-phase rotor shown in FIG. 31 asviewed from its radial direction;

FIG. 33 is a perspective view of an entire three-phase stator;

FIG. 34 is a sectional view of the three-phase stator shown in FIG. 33;

FIG. 35 is a sectional view of a motor according to a fifth embodimentof the present invention;

FIG. 36 is a sectional perspective view of a rotor shown in FIG. 35;

FIG. 37 is an exploded perspective view of the rotor shown in FIG. 36;

FIG. 38 is a sectional view of a rotor in another example of the fifthembodiment;

FIG. 39A is a perspective view of a non-magnetic portion in anotherexample of the fifth embodiment;

FIG. 39B is an explanatory diagram for explaining an assembled state ofthe non-magnetic portion shown in FIG. 39A;

FIG. 40A is a perspective view of a non-magnetic portion in anotherexample of the fifth embodiment;

FIG. 40B is an explanatory diagram for explaining an assembled state ofthe non-magnetic portion shown in FIG. 40A;

FIG. 41A is a perspective view of a non-magnetic portion in anotherexample of the fifth embodiment;

FIG. 41B is an explanatory diagram for explaining an assembled state ofthe non-magnetic portion shown in FIG. 41A;

FIG. 42 is a sectional view of a motor of a multi-Lundell type structureaccording to a sixth embodiment of the present invention;

FIG. 43 is an explanatory diagram showing change in an average torquewith respect to change in a ratio of thicknesses of a main magnet and anauxiliary magnet shown in FIG. 42;

FIG. 44 is an explanatory diagram showing change in a ripple factor withrespect to change in a ratio of thicknesses of the main magnet and theauxiliary magnet shown in FIG. 42;

FIG. 45 is a perspective view of a motor according to a seventhembodiment of the present invention;

FIG. 46 is a perspective view of a rotor shown in FIG. 45;

FIG. 47 is an exploded perspective view of a single rotor shown in FIG.46;

FIG. 48 is a schematic diagram for explaining a producing mode of therotor shown in FIG. 47;

FIG. 49 is a schematic diagram for explaining a producing mode of therotor shown in FIG. 47;

FIG. 50 is a perspective view of a rotor in another example of theseventh embodiment;

FIG. 51 is a perspective view of a motor according to an eighthembodiment of the present invention;

FIG. 52 is a perspective view of a rotor shown in FIG. 51;

FIG. 53 is a side view of the rotor shown in FIG. 52;

FIG. 54 is an exploded perspective view of the rotor shown in FIG. 52;

FIG. 55 is a plan view of a single rotor (U-phase rotor) and a singlestator (U-phase stator);

FIG. 56 is a combined sectional view taken along line A-B-C in FIG. 55;

FIG. 57 is a perspective view of the rotor shown in FIG. 51;

FIG. 58 is a perspective view of a stator shown in FIG. 51;

FIG. 59 is a sectional view of the stator shown in FIG. 58;

FIG. 60 is a perspective view of a single stator shown in FIG. 58;

FIG. 61 is an exploded perspective view of the single stator shown inFIG. 60;

FIG. 62 is a perspective view of a rotor in another example of theeighth embodiment;

FIG. 63 is a perspective view of an outer peripheral member in anotherexample of the eighth embodiment;

FIG. 64 is a perspective view of an outer peripheral member in anotherexample of the eighth embodiment;

FIG. 65 is a perspective view of a motor according to a ninth embodimentof the present invention;

FIG. 66 is a perspective view showing a single stator shown in FIG. 65;

FIG. 67 is a schematic diagram for explaining a producing mode of astator core shown in FIG. 66;

FIG. 68 is a perspective view showing a single stator of another exampleof the ninth embodiment;

FIG. 69 is a schematic diagram for explaining a producing mode of astator core shown in FIG. 68;

FIG. 70 is a perspective view showing a single stator of another exampleof the ninth embodiment;

FIG. 71 is a schematic diagram for explaining a producing mode of astator core shown in FIG. 70;

FIG. 72 is a perspective view of a motor according to a tenth embodimentof the present invention;

FIG. 73 is an exploded perspective view of a yoke housing and a statorshown in FIG. 72;

FIG. 74 is a partially sectional perspective view of the stator shown inFIG. 73;

FIG. 75 is a plan view partially showing the stator and the yoke housingshown in FIG. 73;

FIG. 76 is a perspective view partially showing a stator (U-phasestator) shown in FIG. 73;

FIG. 77 is a perspective view partially showing a stator core and a yokehousing of another example of the tenth embodiment;

FIG. 78 is a perspective view partially showing a stator (one phase)according to an eleventh embodiment of the present invention;

FIG. 79 is a perspective view partially showing a stator (one phase) ofanother example of the eleventh embodiment.

FIG. 80 is a sectional view schematically showing a portion of a state(one phase) in another example of the eleventh embodiment;

FIG. 81 is a perspective view showing a winding fixing member(interposed member) in another example of FIG. 80;

FIG. 82 is a perspective view showing a winding fixing member of anotherexample of the eleventh embodiment;

FIG. 83 is a perspective view showing an opened state of a windingfixing member of another example of FIG. 82;

FIG. 84 is a perspective view of a motor according to a twelfthembodiment of the present invention;

FIG. 85 is an exploded perspective view of a single stator shown in FIG.84;

FIG. 86 is a plan view of a stator core and a coil shown in FIG. 85;

FIG. 87 is a plan view of a stator core and a coil of another example ofthe twelfth embodiment;

FIG. 88A is a plan view of a stator core and a rotor core of anotherexample of the twelfth embodiment;

FIG. 88B is an enlarged view of a claw-shaped magnetic pole shown inFIG. 88A; and

FIG. 89 is a plan view of a stator core of another example of thetwelfth embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

A first embodiment of a motor will be described in accordance with FIGS.1 to 14.

As shown in FIGS. 1 and 2, a three-phase brushless motor M includes arotor 1 fixed to a rotation shaft (not shown), and an annular stator 2placed outside of the rotor 1 and fixed to a motor housing (not shown).

As shown in FIGS. 3 to 6, the brushless motor M is a three-phase motorin which three single motors Ma each including a single rotor 1 a and asingle stator 2 a are stacked on one another. That is, as shown in FIG.2, a single motor Ma of a U-phase motor portion Mu, a single motor Ma ofa V-phase motor portion My and a single motor Ma of a W-phase motorportion Mw are stacked on one another in this order from above.

(Rotor 1)

As shown in FIGS. 9 to 11, the rotor 1 includes three rotors, i.e., aU-phase rotor 1 u, a V-phase rotor 1 v and a W-phase rotor 1 w. In thefirst embodiment, the three-phase rotors 1 u, 1 v and 1 w have the sameconfigurations. When the rotors 1 u, 1 v and 1 w of the phases arecollectively called, they will be called as a single rotor 1 a for thesake of convenience.

As shown in FIGS. 5A and 7, the single rotor 1 a includes first tofourth four rotor cores 10, 20, 30 and 40 and first to fourth four fieldmagnets 51, 52, 53 and 54.

(First Rotor Core 10)

As shown in FIG. 7, the first rotor core 10 includes a first rotor corebase 11 formed from a disk-shaped electromagnetic steel plate. A throughhole 12 is formed in a central position of the first rotor core base 11,and a rotation shaft (not shown) is inserted through and fixed to thethrough hole 12. On the outer peripheral surface of the first rotor corebase 11, twelve first rotor-side claw-shaped magnetic poles 13 areformed at equal intervals from one another. The twelve first rotor-sideclaw-shaped magnetic poles 13 project radially outward from the outerperipheral surface of the first rotor core base 11, and tip ends of thepoles 13 bend and extend toward the second rotor core 20 along an axialdirection of the rotor 1.

Circumferential both end surfaces of each of the first rotor-sideclaw-shaped magnetic poles 13 are flat surfaces, and the firstrotor-side claw-shaped magnetic pole 13 is tapered toward its tip end asviewed from a radial direction of the rotor 1. A radial outer surfaceand a radial inner surface of the first rotor-side claw-shaped magneticpole 13 which bends toward the second rotor core 20 along the axialdirection are arc surfaces which form concentric circles centering on acenter axis O of the rotation shaft (not shown). Therefore, a tip endsurface 16 of each of the first rotor-side claw-shaped magnetic poles 13is a flat surface extending in a direction intersecting with the axialdirection at right angles, and is an arc surface which is curved towardthe center axis O as viewed from the axial direction.

A length of the first rotor-side claw-shaped magnetic pole 13 in theaxial direction (length between the tip end surface 16 and a surface ofthe first rotor core base 11 opposite from a surface thereof which facesthe second rotor core 20) is three times of a thickness (length in axialdirection) of the first rotor core base 11.

An angle of the first rotor-side claw-shaped magnetic pole 13 in thecircumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft (not shown) is set smaller than an angle of a gapbetween the first rotor-side claw-shaped magnetic poles 13 which areadjacent to each other.

(Second Rotor Core 20)

As shown in FIGS. 5A and 7, the second rotor core 20 is placed such thatit faces the first rotor core 10 in the axial direction through thefirst field magnet 51. The second rotor core 20 is made of the samematerial and has the same shape as those of the first rotor core 10. Athrough hole 22 is formed in a central position of a substantiallydisk-shaped second rotor core base 21, and the rotation shaft (notshown) is inserted through and fixed to the through hole 22.

On an outer peripheral surface of the second rotor core base 21, twelvesecond rotor-side claw-shaped magnetic poles 23 are formed at equalintervals from one another like the first rotor core 10. The twelvesecond rotor-side claw-shaped magnetic poles 23 project radially outwardfrom the outer peripheral surface of the second rotor core base 21, tipends of which bend and extend toward the third rotor core 30 along theaxial direction.

Circumferential both end surfaces of each of the second rotor-sideclaw-shaped magnetic poles 23 are flat surfaces, and the secondrotor-side claw-shaped magnetic pole 23 is tapered toward its tip end asviewed from the radial direction. A radial outer surface and a radialinner surface of the second rotor-side claw-shaped magnetic pole 23which bends toward the third rotor core 30 along the axial direction arearc surfaces which form concentric circles centering on the center axisO of the rotation shaft. Therefore, a tip end surface 26 of each of thesecond rotor-side claw-shaped magnetic poles 23 is a flat surfaceextending in a direction intersecting with the axial direction at rightangles, and is an arc surface which is curved toward the center axis Oas viewed from the axial direction.

A length of the second rotor-side claw-shaped magnetic pole 23 in theaxial direction (length between the tip end surface 26 and a surface ofthe second rotor core base 21 opposite from a surface thereof whichfaces the third rotor core 30) is three times of a thickness (length inaxial direction) of the second rotor core base 21.

An angle of the second rotor-side claw-shaped magnetic pole 23 in thecircumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thesecond rotor-side claw-shaped magnetic poles 23 which are adjacent toeach other.

The second rotor core base 21 is assembled together with the first rotorcore base 11 such that the twelve second rotor-side claw-shaped magneticpoles 23 are placed at intermediate positions between the twelve firstrotor-side claw-shaped magnetic poles 13 as viewed from the axialdirection.

(Third Rotor Core 30)

As shown in FIGS. 5A and 7, the third rotor core 30 is placed such thatit faces the second rotor core 20 in the axial direction through thesecond and third field magnets 52 and 53. The third rotor core 30 ismade of the same material and has the same shape as those of the firstrotor core 10. A through hole 32 is formed in a central position of asubstantially disk-shaped third rotor core base 31, and the rotationshaft (not shown) is inserted through and fixed to the through hole 32.

On an outer peripheral surface of the third rotor core base 31, twelvethird rotor-side claw-shaped magnetic poles 33 are formed at equalintervals from one another. The twelve third rotor-side claw-shapedmagnetic poles 33 project radially outward from the outer peripheralsurface of the third rotor core base 31, tip ends of which bend andextend toward the second rotor core 20 along the axial direction.

Circumferential both end surfaces of each of the third rotor-sideclaw-shaped magnetic poles 33 are flat surfaces, and the thirdrotor-side claw-shaped magnetic pole 33 is tapered toward its tip end asviewed from the radial direction. A radial outer surface and a radialinner surface of the third rotor-side claw-shaped magnetic pole 33 whichbends toward the second rotor core 20 along the axial direction are arcsurfaces which form concentric circles centering on the center axis O ofthe rotation shaft. Therefore, a tip end surface 36 of each of the thirdrotor-side claw-shaped magnetic poles 33 is a flat surface extending ina direction intersecting with the axial direction at right angles, andis an arc surface which is curved toward the center axis O as viewedfrom the axial direction.

A length of the third rotor-side claw-shaped magnetic pole 33 in theaxial direction (length between the tip end surface 36 and a surface ofthe third rotor core base 31 opposite from the surface thereof whichfaces the second rotor core 20) is three times of a thickness (length inaxial direction) of the third rotor core base 31.

An angle of the third rotor-side claw-shaped magnetic pole 33 in thecircumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thethird rotor-side claw-shaped magnetic poles 33 which are adjacent toeach other.

The third rotor core base 31 is assembled together with the first rotorcore base 11 such that the twelve third rotor-side claw-shaped magneticpoles 33 are placed such that they are faced to the corresponding twelvefirst rotor-side claw-shaped magnetic poles 13 as viewed from the axialdirection.

Therefore, each of sets of the mutually opposed first rotor-sideclaw-shaped magnetic poles 13 and third rotor-side claw-shaped magneticpoles 33 is bent such that the pole 13 and the pole 33 are faced to eachother in the axial direction. As a result, entire surfaces of the tipend surfaces 16 of the first rotor-side claw-shaped magnetic poles 13and entire surfaces of the tip end surfaces 36 of the third rotor-sideclaw-shaped magnetic poles 33 abut against each other in the axialdirection.

(Fourth Rotor Core 40)

As shown in FIGS. 5A and 7, the fourth rotor core 40 is placed such thatit faces the third rotor core 30 in the axial direction through thefourth field magnet 54. The fourth rotor core 40 is made of the samematerial and has the same shape as those of the first rotor core 10. Athrough hole 42 is formed in a central position of a substantiallydisk-shaped fourth rotor core base 41, and the rotation shaft (notshown) is inserted through and fixed to the through hole 42.

On an outer peripheral surface of the fourth rotor core base 41, twelvefourth rotor-side claw-shaped magnetic poles 43 are formed at equalintervals from one another. The twelve fourth rotor-side claw-shapedmagnetic poles 43 project radially outward from the outer peripheralsurface of the fourth rotor core base 41, tip ends of which bend andextend toward the third rotor core 30 along the axial direction.

Circumferential both end surfaces of each of the fourth rotor-sideclaw-shaped magnetic poles 43 are flat surfaces, and the fourthrotor-side claw-shaped magnetic pole 43 is tapered toward its tip end asviewed from the radial direction. A radial outer surface and a radialinner surface of the fourth rotor-side claw-shaped magnetic pole 43which bends toward the third rotor core 30 along the axial direction arearc surfaces which form concentric circles centering on the center axisO of the rotation shaft. Therefore, tip end surface 46 of each of thefourth rotor-side claw-shaped magnetic poles 43 is a flat surfaceextending in a direction intersecting with the axial direction at rightangles, and is an arc surface which is curved toward the center axis Oas viewed from the axial direction.

A length of the fourth rotor-side claw-shaped magnetic pole 43 in theaxial direction (length between the tip end surface 46 and a surface ofthe fourth rotor core base 41 opposite from a surface thereof whichfaces the third rotor core 30) is three times of a thickness (length inaxial direction) of the fourth rotor core base 41.

An angle of the fourth rotor-side claw-shaped magnetic pole 43 in thecircumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thefourth rotor-side claw-shaped magnetic poles 43 which are adjacent toeach other.

The fourth rotor core base 41 is assembled together with the secondrotor core base 21 such that the twelve fourth rotor-side claw-shapedmagnetic poles 43 are placed such that they are faced to thecorresponding twelve second rotor-side claw-shaped magnetic poles 23 asviewed from the axial direction.

Therefore, each of sets of the mutually opposed second rotor-sideclaw-shaped magnetic poles 23 and fourth rotor-side claw-shaped magneticpoles 43 is bent such that the pole 23 and the pole 43 are faced to eachother in the axial direction. As a result, entire surfaces of the tipend surfaces 26 of the second rotor-side claw-shaped magnetic poles 23and entire surfaces of the tip end surfaces 46 of the fourth rotor-sideclaw-shaped magnetic poles 43 abut against each other in the axialdirection.

A magnetic pole of each of sets of the first rotor-side claw-shapedmagnetic poles 13 and the third rotor-side claw-shaped magnetic poles 33and a magnetic pole of each of sets of the second rotor-side claw-shapedmagnetic poles 23 and the fourth rotor-side claw-shaped magnetic poles43 are determined by the first to fourth field magnets 51 to 54 placedbetween the first to fourth rotor cores 10, 20, 30 and 40.

(First to Fourth Field Magnets 51 to 54)

As shown in FIG. 7, in the first embodiment, the first to fourth fieldmagnets 51 to 54 are formed from disk-shaped permanent magnets each madeof ferrite magnet, and through holes 56 to 59 are formed in centralpositions of the field magnets 51 to 54, and the rotation shaft (notshown) is inserted through the through holes.

Outer diameters of the first to fourth field magnets 51 to 54 coincidewith outer diameters of the first to fourth rotor core bases 11, 21, 31and 41. Thicknesses (lengths in axial direction) of the first to fourthfield magnets 51 to 54 coincide with thicknesses (lengths in axialdirection) of the first to fourth rotor core bases 11, 21, 31 and 41.

As shown in FIGS. 5A and 7, the first field magnet 51 is stacked betweenthe first rotor core 10 and the second rotor core 20. The second fieldmagnet 52 and the third field magnet 53 are stacked between the secondrotor core 20 and the third rotor core 30. The fourth field magnet 54 isstacked between the third rotor core 30 and the fourth rotor core 40.

As described above, a length of each of the first to fourth rotor-sideclaw-shaped magnetic poles 13, 23, 33 and 43 in the axial direction isthree times of the thickness (length in axial direction) of each of thefirst to fourth rotor core bases 11, 21, 31 and 41. According to this,when the first to fourth rotor cores 10, 20, 30 and 40 are stacked onone another in the axial direction through the first to fourth fieldmagnets 51 to 54, the tip end surfaces 16 of the first rotor-sideclaw-shaped magnetic poles 13 and the tip end surfaces 36 of the thirdrotor-side claw-shaped magnetic poles 33 abut against each other.Similarly, the tip end surfaces 26 of the second rotor-side claw-shapedmagnetic poles 23 and the tip end surfaces 46 of the fourth rotor-sideclaw-shaped magnetic poles 43 abut against each other.

(First Field Magnet 51)

The first field magnet 51 is magnetized in the axial direction such thata portion thereof (first portion) closer to the first rotor core 10becomes north pole and a portion thereof (second portion) closer to thesecond rotor core 20 becomes south pole. Therefore, by this first fieldmagnet 51, the first rotor-side claw-shaped magnetic poles 13 of thefirst rotor core 10 function as north poles (first magnetic poles), andthe second rotor-side claw-shaped magnetic poles 23 of the second rotorcore 20 function as south poles (second magnetic poles).

(Second Field Magnet 52)

The second field magnet 52 is magnetized in the axial direction suchthat a portion thereof (first portion) closer to the second rotor core20 becomes south pole and a portion thereof (second portion) closer tothe third field magnet 53 becomes north pole. Therefore, by this secondfield magnet 52, the second rotor-side claw-shaped magnetic poles 23 ofthe second rotor core 20 function as south poles (second magneticpoles). That is, the second rotor-side claw-shaped magnetic poles 23 ofthe second rotor core 20 become south poles by the second field magnet52 and the first field magnet 51.

(Third Field Magnet 53)

The third field magnet 53 is magnetized in the axial direction such thata portion thereof (first portion) closer to the second field magnet 52becomes south pole and a portion thereof (second portion) closer to thethird rotor core 30 becomes north pole. Therefore, by this third fieldmagnet 53, the third rotor-side claw-shaped magnetic poles 33 of thethird rotor core 30 function as north poles (first magnetic poles).

(Fourth Field Magnet 54)

The fourth field magnet 54 is magnetized in the axial direction suchthat a portion thereof (first portion) closer to the third rotor core 30becomes north pole and a portion thereof (second portion) closer to thefourth rotor core 40 becomes south pole. Therefore, by this fourth fieldmagnet 54, the third rotor-side claw-shaped magnetic poles 33 of thethird rotor core 30 function as north poles (first magnetic poles), andthe fourth rotor-side claw-shaped magnetic poles 43 of the fourth rotorcore 40 function as south poles (second magnetic poles). That is, thethird rotor-side claw-shaped magnetic poles 33 of the third rotor core30 become north poles by the fourth field magnet 54 and the third fieldmagnet 53.

Further, since the tip end surfaces 36 of the third rotor-sideclaw-shaped magnetic poles 33 and the tip end surfaces 16 of thecorresponding first rotor-side claw-shaped magnetic poles 13 abutagainst each other in the axial direction, the sets of mutually opposedfirst rotor-side claw-shaped magnetic poles 13 and third rotor-sideclaw-shaped magnetic poles 33 become north poles.

Similarly, since the tip end surfaces 46 of the fourth rotor-sideclaw-shaped magnetic poles 43 and the tip end surfaces 26 of the secondrotor-side claw-shaped magnetic poles 23 abut against each other in theaxial direction, the sets of mutually opposed second rotor-sideclaw-shaped magnetic poles 23 and fourth rotor-side claw-shaped magneticpole 43 become south poles.

The single rotor 1 a configured in this manner is a rotor of so-calledLundell type structure using the first to fourth four rotor cores 10,20, 30 and 40 and the first to fourth four field magnets 51 to 54. Inthe single rotor 1 a, sets of the first rotor-side claw-shaped magneticpoles 13 and the third rotor-side claw-shaped magnetic poles 33 whichbecome north poles, and sets of the second rotor-side claw-shapedmagnetic poles 23 and the fourth rotor-side claw-shaped magnetic poles43 which become south poles are alternately placed in thecircumferential direction, and the number of magnetic poles is twentyfour (the number of pairs of poles is twelve).

As shown in FIGS. 9 to 11, the single rotors 1 a are used as a U-phaserotor 1 u, a V-phase rotor 1 v and a W-phase rotor 1 w and these rotors1 u, 1 v and 1 w are stacked on one another in the axial direction toform the three-phase rotor 1.

More specifically, the U-phase rotor 1 u, the V-phase rotor 1 v and theW-phase rotor 1 w are stacked on one another in this order as shown inFIG. 11. The U-phase rotor 1 u and the W-phase rotor 1 w are placed suchthat placement directions of the first to fourth rotor cores 10, 20, 30and 40 (first to fourth field magnets 51 to 54) become the same.

On the other hand, as shown in FIG. 11, the V-phase rotor 1 v which isstacked between the U-phase rotor 1 u and the W-phase rotor 1 w isplaced such that placement directions of the first to fourth rotor cores10, 20, 30 and 40 (first to fourth field magnets 51 to 54) becomeopposite from the placement directions of the first to fourth rotorcores 10, 20, 30 and 40 (first to fourth field magnets 51 to 54) of theU-phase rotor 1 u and the W-phase rotor 1 w.

That is, the V-phase rotor 1 v is stacked between the U-phase rotor 1 uand the W-phase rotor 1 w such that the fourth rotor core 40 of theV-phase rotor 1 v and the fourth rotor core 40 of the U-phase rotor 1 uabut against each other, and the first rotor core 10 of the V-phaserotor 1 v and the first rotor core 10 of the W-phase rotor 1 w abutagainst each other.

At this time, as shown in FIG. 10, the U-phase rotor 1 u, the V-phaserotor 1 v and the W-phase rotor 1 w configuring the three-phase rotor 1are stacked on one another such that these rotors 1 u, 1 v and 1 w aredisplaced from one another by 5° in mechanical angle (60° in electricalangle).

More specifically, the V-phase rotor 1 v is fixed to the rotation shaftin a state where the V-phase rotor 1 v is displaced from the U-phaserotor 1 u by 5° in machine angle (60° in electrical angle) around thecenter axis O of the rotation shaft in the counterclockwise direction asviewed from the U-phase rotor 1 u. The W-phase rotor 1 w is fixed to therotation shaft in a state where the W-phase rotor 1 w is displaced fromthe V-phase rotor 1 v by 5° in mechanical angle (60° in electricalangle) around the center axis O of the rotation shaft in thecounterclockwise direction as viewed from the V-phase rotor 1 v.

(Stator 2)

As shown in FIGS. 12 and 13, the stator 2 which is placed at a radiallyoutside of the three-phase rotor 1 includes three stators, i.e., aU-phase stator 2 u, a V-phase stator 2 v and a W-phase stator 2 w. Thestators 2 u, 2 v and 2 w are stacked on one another in this order in theaxial direction such that the stators 2 u, 2 v and 2 w face the U-phaserotor 1 u, the V-phase rotor 1 v and the W-phase rotor 1 w whichrespectively correspond to the stators 2 u, 2 v and 2 w in the radialdirection.

The stators 2 u, 2 v and 2 w have the same configurations. For the sakeof convenience of description, when the stators 2 u, 2 v and 2 w of thephases are collectively called, they will be called a single stator 2 a.

As shown in FIGS. 5B and 8, the single stator 2 a includes first tofourth four stator cores 60, 70, 80 and 90, and first to fourth fourannular windings 101, 102, 103 and 104.

(First Stator Core 60)

As shown in FIG. 8, the first stator core 60 includes a first statorcore base 61 formed from an annular electromagnetic steel plate. A firstcylindrical wall 62 is formed on an outer periphery of the first statorcore base 61. The first cylindrical wall 62 extends from a surface ofthe first stator core base 61 which faces the second stator core 70 ofthe first stator core base 61 along the axial direction toward thesecond stator core 70. This extending length of the first cylindricalwall 62 corresponds to a thickness of the first stator core base 61. Anouter peripheral surface of the first cylindrical wall 62 abuts againstand is fixed to an inner surface of a motor housing (not shown). Anannular tip end surface 63 of the first cylindrical wall 62 abutsagainst second stator core bases 71 of the second stator core 70.

On the other hand, on an inner peripheral surface of the first statorcore base 61, twelve first stator-side claw-shaped magnetic poles 64 areformed at equal intervals. The twelve first stator-side claw-shapedmagnetic poles 64 extend radially inward from the inner peripheralsurface of the first stator core base 61 and then, bend and extendtoward the second stator core 70 along the axial direction.

Circumferential both end surfaces of each of the first stator-sideclaw-shaped magnetic poles 64 are flat surfaces, and the firststator-side claw-shaped magnetic pole 64 is tapered toward its tip endas viewed from the radial direction. A radial outer surface and a radialinner surface of the first stator-side claw-shaped magnetic pole 64which bends toward the second stator core 70 along the axial directionare arc surfaces which become concentric circles centering on the centeraxis O of the rotation shaft. Therefore, a tip end surface 67 of each ofthe first stator-side claw-shaped magnetic poles 64 is a flat surfaceextending in a direction intersecting with the axial direction at rightangles, and is an arc surface which is curved toward the center axis Oas viewed from the axial direction.

A length (length between the tip end surface 67 and a surface of thefirst stator core base 61 opposite from a surface thereof which facesthe second stator core 70) of the first stator-side claw-shaped magneticpole 64 in the axial direction is three times of a thickness (length inaxial direction) of the first stator core base 61.

An angle of each of the first stator-side claw-shaped magnetic poles 64in the circumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thefirst stator-side claw-shaped magnetic poles 64 which are adjacent toeach other.

(Second Stator Core 70)

As shown in FIG. 8, the second stator core 70 includes an annularplate-shaped second stator core base 71 made of the same material andhaving the same shape as those of the first stator core 60. Acylindrical second cylindrical wall 72 is formed on an outer peripheryof the second stator core bases 71. The second cylindrical wall 72extends from a surface of the second stator core base 71 which faces thethird stator core 80 toward the third stator core 80 along the axialdirection, and this extending length of the second cylindrical wall 72corresponds to a thickness of the second stator core base 71. An outerperipheral surface of the second cylindrical wall 72 abuts against andis fixed to an inner surface of the motor housing (not shown). Anannular tip end surface 73 of the second cylindrical wall 72 abutsagainst a tip end surface 83 of the third cylindrical wall 82 of thethird stator core 80.

On the other hand, on an inner peripheral surface of the second statorcore base 71, twelve second stator-side claw-shaped magnetic poles 74are formed at equal intervals. The twelve second stator-side claw-shapedmagnetic poles 74 extend radially inward from the inner peripheralsurface of the second stator core base 71 and then, bend and extendtoward the third stator core 80 along the axial direction.

Circumferential both end surfaces of each of the second stator-sideclaw-shaped magnetic poles 74 are flat surfaces, and the secondstator-side claw-shaped magnetic pole 74 is tapered toward its tip endas viewed from the radial direction. A radial outer surface and a radialinner surface of the second stator-side claw-shaped magnetic pole 74which bends toward the third stator core 80 along the axial directionare arc surfaces which become concentric circles centering on the centeraxis O of the rotation shaft. Therefore, a tip end surface 77 of each ofthe second stator-side claw-shaped magnetic poles 74 is a flat surfaceextending in a direction intersecting with the axial direction at rightangles, and is an arc surface which is curved toward the center axis Oas viewed from the axial direction.

A length (length between the tip end surface 77 and a surface of thesecond stator core base 71 opposite from a surface thereof which facesthe third stator core 80) of the second stator-side claw-shaped magneticpole 74 in the axial direction is three times of a thickness (length inaxial direction) of the second stator core base 71.

An angle of each of the second stator-side claw-shaped magnetic poles 74in the circumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thesecond stator-side claw-shaped magnetic poles 74 which are adjacent toeach other.

The second stator core 70 is fixed to the first stator core 60 such thatthe second stator-side claw-shaped magnetic poles 74 of the secondstator core 70 are placed at intermediate positions between the firststator-side claw-shaped magnetic poles 64 as viewed from the axialdirection.

Since the annular tip end surface 63 of the first cylindrical wall 62formed on the first stator core 60 abuts against the outer periphery ofthe second stator core base 71 of the second stator core 70, an annularspace is formed between the first stator core base 61 and the secondstator core base 71. The first annular winding 101 is wound and placedin the annular space.

(Third Stator Core 80)

As shown in FIG. 8, the third stator core 80 includes an annularplate-shaped third stator core base 81 made of the same material andhaving the same shape as those of the first stator core 60. Acylindrical third cylindrical wall 82 is formed on an outer periphery ofthe third stator core base 81. The third cylindrical wall 82 extendsfrom a surface of the third stator core base 81 which faces the secondstator core 70 toward the second stator core 70 along the axialdirection, and this extending length of the third cylindrical wall 82corresponds to a thickness of the third stator core base 81. An outerperipheral surface of the third cylindrical wall 82 abuts against and isfixed to an inner surface of the motor housing (not shown). An annulartip end surface 83 of the third cylindrical wall 82 abuts against a tipend surface 73 of the second cylindrical wall 72 of the second statorcore 70.

On the other hand, on an inner peripheral surface of the third statorcore base 81, twelve third stator-side claw-shaped magnetic poles 84 areformed at equal intervals. The twelve third stator-side claw-shapedmagnetic poles 84 extend radially inward from the inner peripheralsurface of the third stator core base 81 and then, bend and extendtoward the second stator core 70 along the axial direction.

Circumferential both end surfaces of each of the third stator-sideclaw-shaped magnetic poles 84 are flat surfaces, and the thirdstator-side claw-shaped magnetic pole 84 is tapered toward its tip endas viewed from the radial direction. A radial outer surface and a radialinner surface of the third stator-side claw-shaped magnetic pole 84which bends toward the second stator core 70 along the axial directionare arc surfaces which become concentric circles centering on the centeraxis O of the rotation shaft. Therefore, a tip end surface 87 of each ofthe third stator-side claw-shaped magnetic poles 84 is a flat surfaceextending in a direction intersecting with the axial direction at rightangles, and is an arc surface which is curved toward the center axis Oas viewed from the axial direction.

A length (length between the tip end surface 87 and a surface of thethird stator core base 81 opposite from a surface thereof which facesthe second stator core 70) of the third stator-side claw-shaped magneticpole 84 in the axial direction is three times of a thickness (length inaxial direction) of the third stator core base 81.

An angle of each of the third stator-side claw-shaped magnetic poles 84in the circumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thethird stator-side claw-shaped magnetic poles 84 which are adjacent toeach other.

The third stator core 80 is placed on and fixed to the first stator core60 such that the first stator-side claw-shaped magnetic poles 64 of thefirst stator core 60 face the corresponding third stator-sideclaw-shaped magnetic poles 84 as viewed from the axial direction. Entiresurfaces of the tip end surfaces 67 of the first stator-side claw-shapedmagnetic poles 64 and entire surfaces of the tip end surfaces 87 of thethird stator-side claw-shaped magnetic poles 84 faces to each other inthe axial direction and abut against each other.

Here, the annular tip end surface 73 of the second cylindrical wall 72and the annular tip end surface 83 of the third cylindrical wall 82 abutagainst each other, and the tip end surfaces 67 of the first stator-sideclaw-shaped magnetic poles 64 and the tip end surfaces 87 of the thirdstator-side claw-shaped magnetic poles 84 abut against each other.Therefore, an annular space is formed between the second stator corebase 71 and the third stator core base 81. An axial length of thisannular space is two times of an axial length of an annular space formedbetween the first stator core base 61 and the second stator core base71. This is because that the annular space formed between the firststator core base 61 and the second stator core base 71 is determined bythe axial length of the first cylindrical wall 62, while the annularspace formed between the second stator core base 71 and the third statorcore base 81 is determined by axial lengths of the second cylindricalwall 72 and the third cylindrical wall 82.

The second annular winding 102 is wound and placed in a portion of thisannular space closer to the second stator core base 71, and the thirdannular winding 103 is wound and placed in a portion of this annularspace closer to the third stator core base 81.

(Fourth Stator Core 90)

As shown in FIG. 8, the fourth stator core 90 includes an annularplate-shaped fourth stator core base 91 made of the same material andhaving the same shape as those of the first stator core 60. Acylindrical fourth cylindrical wall 92 is formed on an outer peripheryof the fourth stator core base 91. The fourth cylindrical wall 92extends from a surface of the fourth stator core base 91 which faces thethird stator core 80 toward the third stator core 80 along the axialdirection, and this extending length of the fourth cylindrical wall 92corresponds to a thickness of the fourth stator core base 91. An outerperipheral surface of the fourth cylindrical wall 92 abuts against andis fixed to an inner surface of the motor housing (not shown). Anannular tip end surface 93 of the fourth cylindrical wall 92 abutsagainst the third stator core base 81 of the third stator core 80.

On the other hand, on an inner peripheral surface of the fourth statorcore base 91, twelve fourth stator-side claw-shaped magnetic poles 94are formed at equal intervals from one another. The twelve fourthstator-side claw-shaped magnetic poles 94 extend radially inward fromthe inner peripheral surface of the fourth stator core base 91 and then,bend and extend toward the third stator core 80 along the axialdirection.

Circumferential both end surfaces of each of the fourth stator-sideclaw-shaped magnetic poles 94 are flat surfaces, and the fourthstator-side claw-shaped magnetic pole 94 is tapered toward its tip endas viewed from the radial direction. A radial outer surface and a radialinner surface of the fourth stator-side claw-shaped magnetic pole 94which bends toward the third stator core 80 along the axial directionare arc surfaces which become concentric circles centering on the centeraxis O of the rotation shaft. Therefore, a tip end surface 97 of each ofthe fourth stator-side claw-shaped magnetic poles 94 is a flat surfaceextending in a direction intersecting with the axial direction at rightangles, and is an arc surface which is curved toward the center axis Oas viewed from the axial direction.

A length (length between the tip end surface 97 and a surface of thefourth stator core base 91 opposed to a surface thereof which faces thethird stator core 80) of the fourth stator-side claw-shaped magneticpole 94 in the axial direction is three times of a thickness (length inaxial direction) of the fourth stator core base 91.

An angle of each of the fourth stator-side claw-shaped magnetic poles 94in the circumferential direction, i.e., an angle formed between both endsurfaces thereof in the circumferential direction and the center axis Oof the rotation shaft is set smaller than an angle of a gap between thefourth stator-side claw-shaped magnetic poles 94 which are adjacent toeach other.

The fourth stator core 90 is placed on and fixed to the second statorcore 70 such that the second stator-side claw-shaped magnetic poles 74of the second stator core 70 face the corresponding fourth stator-sideclaw-shaped magnetic poles 94 as viewed from the axial direction. Entiresurfaces of the tip end surfaces 77 of the second stator-sideclaw-shaped magnetic poles 74 and entire surfaces of the tip endsurfaces 97 of the fourth stator-side claw-shaped magnetic poles 94 faceand abut against each other in the axial direction.

Since the annular tip end surface 93 of the fourth cylindrical wall 92formed on the fourth stator core 90 abuts against the outer periphery ofthe third stator core base 81 of the third stator core 80, an annularspace is formed between the third stator core base 81 and the fourthstator core base 91. The fourth annular winding 104 is wound and placedin this annular space.

(First to Fourth Annular Windings 101 to 104)

As shown in FIGS. 5B and 8, the first annular winding 101 is sandwichedbetween the first stator core base 61 and the second stator core base71. The second annular winding 102 and the third annular winding 103 aresandwiched between the second stator core base 71 and the third statorcore base 81. The second annular winding 102 is placed in a space closerto the second stator core base 71, and the third annular winding 103 isplaced in a space closer to the third stator core base 81. The fourthannular winding 104 is sandwiched between the third stator core base 81and the fourth stator core base 91.

The first to fourth annular windings 101 to 104 are connected to oneanother in series, and the windings 101 to 104 have the same windingnumber (number of windings, or winding times). The first annular winding101 and the fourth annular winding 104 are wound in a normal direction.The second annular winding 102 and the third annular winding 103 arewound in a direction opposite from the normal direction of the firstannular winding 101 and the fourth annular winding 104.

(First Annular Winding 101)

As shown in FIGS. 5B and 8, the first annular winding 101 is an annularwinding, and is placed in an annular space formed between the firststator core base 61 and the second stator core base 71. An outerdiameter of the first annular winding 101 is substantially equal to aninner diameter of the first cylindrical wall 62, and the first annularwinding 101 is placed such that an outer peripheral surface thereof inthe radial direction abuts against an inner peripheral surface of thefirst cylindrical wall 62. An inner diameter of the first annularwinding 101 is substantially equal to an outer diameter of the firststator-side claw-shaped magnetic poles 64. The first annular winding 101is placed such that a radial inner surface thereof abuts against outersurfaces of the first stator-side claw-shaped magnetic poles 64.

An outer surface of the first annular winding 101 which faces the firststator core 60 in the axial direction abuts against the first statorcore bases 61, and an outer surface of the first annular winding 101which faces the second stator core 70 in the axial direction abutsagainst the second stator core base 71.

A length of the first annular winding 101 in the axial directioncoincides with a thickness (length of first cylindrical wall 62 in axialdirection) of the first stator core 60.

(Second Annular Winding 102)

As shown in FIGS. 5B and 8, the second annular winding 102 is an annularwinding. The second annular winding 102 is made of the same material andhas the same shape as those of the first annular winding 101. The secondannular winding 102 is placed in a portion of an annular space formedbetween the second stator core base 71 and the third stator core base 81at a location closer to the second stator core base 71.

An outer diameter of the second annular winding 102 is substantiallyequal to an inner diameter of the second cylindrical wall 72, and thesecond annular winding 102 is placed such that an outer peripheralsurface thereof in the radial direction abuts against an innerperipheral surface of the second cylindrical wall 72. An inner diameterof the second annular winding 102 is substantially equal to an outerdiameter of the second stator-side claw-shaped magnetic poles 74. Thesecond annular winding 102 is placed such that a radial inner surfacethereof abuts against outer surfaces of the second stator-sideclaw-shaped magnetic poles 74.

An outer surface of the second annular winding 102 which faces thesecond stator core 70 in the axial direction abuts against the secondstator core base 71, and an outer surface of the second annular winding102 which faces the third stator core 80 in the axial direction abutsagainst the third annular winding 103.

A length of the second annular winding 102 in the axial directioncoincides with a thickness (length of second cylindrical wall 72 inaxial direction) of the second stator core 70.

(Third Annular Winding 103)

As shown in FIGS. 5B and 8, the third annular winding 103 is an annularwinding. The third annular winding 103 is made of the same material andhas the same shape as those of the first annular winding 101. The thirdannular winding 103 is placed in a portion of the annular space formedbetween the second stator core base 71 and the third stator core base 81located at a location closer to the third stator core base 81.

An outer diameter of the third annular winding 103 is substantiallyequal to an inner diameter of the third cylindrical wall 82, and thethird annular winding 103 is placed such that an outer peripheralsurface thereof in the radial direction abuts against an innerperipheral surface of the third cylindrical wall 82. An inner diameterof the third annular winding 103 is substantially equal to an outerdiameter of the third stator-side claw-shaped magnetic poles 84. Thethird annular winding 103 is placed such that a radial inner surfacethereof abuts against outer surfaces of the third stator-sideclaw-shaped magnetic poles 84.

An outer surface of the third annular winding 103 which faces the secondstator core 70 in the axial direction abuts against the second annularwinding 102, and an outer surface of the third annular winding 103 whichfaces the third stator core 80 in the axial direction abuts against thethird stator core base 81.

A length of the third annular winding 103 in the axial directioncoincides with a thickness (length of third cylindrical wall 82 in axialdirection) of the third stator core 80.

(Fourth Annular Winding 104)

As shown in FIGS. 5B and 8, the fourth annular winding 104 is an annularwinding. The fourth annular winding 104 is made of the same material andhas the same shape as those of the first annular winding 101. The fourthannular winding 104 is placed in an annular space formed between thethird stator core base 81 and the fourth stator core base 91.

An outer diameter of the fourth annular winding 104 is substantiallyequal to an inner diameter of the fourth cylindrical wall 92, and thefourth annular winding 104 is placed such that an outer peripheralsurface thereof in the radial direction abuts against an innerperipheral surface of the fourth cylindrical wall 92. An inner diameterof the fourth annular winding 104 is substantially equal to an outerdiameter of the fourth stator-side claw-shaped magnetic poles 94. Thefourth annular winding 104 is placed such that a radial inner surfacethereof abuts against outer surfaces of the fourth stator-sideclaw-shaped magnetic poles 94.

An outer surface of the fourth annular winding 104 which faces the thirdstator core 80 in the axial direction abuts against the third statorcore base 81, and an outer surface of the fourth annular winding 104which faces the fourth stator core 90 in the axial direction abutsagainst the fourth stator core base 91.

A length of the fourth annular winding 104 in the axial directioncoincides with a thickness (length of fourth cylindrical wall 92 inaxial direction) of the fourth stator core 90.

As described above, lengths of the first to fourth stator-sideclaw-shaped magnetic poles 64, 74, 84 and 94 in the axial direction arethree times of thicknesses (lengths in axial direction) of the first tofourth stator core bases 61, 71, 81 and 91. According to this, when thefirst to fourth stator cores 60, 70, 80 and 90 are stacked on oneanother in the axial direction through the first to fourth annularwindings 101 to 104, tip end surfaces 67 of the first stator-sideclaw-shaped magnetic poles 64 and tip end surfaces 87 of the thirdstator-side claw-shaped magnetic poles 84 respectively abut against eachother. Similarly, the tip end surfaces 77 of the second stator-sideclaw-shaped magnetic poles 74 and the tip end surfaces 97 of the fourthstator-side claw-shaped magnetic poles 94 respectively abut against eachother.

As described above, the first and fourth annular windings 101 and 104are wound in the normal direction, and the second and third annularwindings 102 and 103 are wound in the opposite direction. Therefore,when current is made to flow through the first to fourth annularwindings 101 to 104 which are connected to one another in series, adirection of current flowing through the second and third annularwindings 102 and 103 is always opposite from a direction of currentflowing through the first and fourth annular windings 101 and 104.

When single-phase AC current is made to flow through the first to fourthannular windings 101 to 104, the first to fourth stator-side claw-shapedmagnetic poles 64, 74, 84 and 94 are excited to magnetic poles which aredifferent from each other at each timing.

That is, the tip end surfaces 67 of the first stator-side claw-shapedmagnetic poles 64 and the tip end surfaces 87 of the corresponding thirdstator-side claw-shaped magnetic poles 84 respectively abut against eachother, and a magnetic flux density of the magnetic poles varies at thesame timing and with the same cycle. Similarly, the tip end surfaces 77of the second stator-side claw-shaped magnetic poles 74 and the tip endsurfaces 97 of the corresponding fourth stator-side claw-shaped magneticpoles 94 respectively abut against each other, and a magnetic fluxdensity of the magnetic poles varies at the same timing and with thesame cycle.

Further, a variation cycle of a magnetic flux density of the first andthird stator-side claw-shaped magnetic poles 64 and 84 and a variationcycle of a magnetic flux density of the second and fourth stator-sideclaw-shaped magnetic poles 74 and 94 are deviated from each other by180° in phase.

The single stator 2 a configured as described above is a stator of aso-called Lundell type (claw pole type) structure having twenty fourpoles in which sets of the first stator-side claw-shaped magnetic poles64 and the third stator-side claw-shaped magnetic poles 84 and sets ofthe second stator-side claw-shaped magnetic poles 74 and the fourthstator-side claw-shaped magnetic poles 94 are excited into magneticpoles which are different from each other at each timing by the first tofourth stator cores 60, 70, 80 and 90 and the first to fourth annularwindings 101 to 104.

In the first embodiment, thicknesses of the first to fourth stator corebases 61, 71, 81 and 91 and the first to fourth rotor core bases 11, 21,31 and 41 are equal to each other. As a result, lengths of the singlestator 2 a and the single rotor 1 a in the axial direction are the same.

Therefore, in the single motor Ma in which the single rotor 1 a isplaced on the inner side of the single stator 2 a, sets of the firstrotor-side claw-shaped magnetic poles 13 and the third rotor-sideclaw-shaped magnetic poles 33 and sets of the first stator-sideclaw-shaped magnetic poles 64 and the third stator-side claw-shapedmagnetic poles 84 are placed such that they face to each other in theradial direction. Similarly, sets of the second rotor-side claw-shapedmagnetic poles 23 and the fourth rotor-side claw-shaped magnetic poles43 and sets of the second stator-side claw-shaped magnetic poles 74 andthe fourth stator-side claw-shaped magnetic poles 94 are placed suchthat they face to each other in the radial direction.

As shown in FIGS. 12 and 13, the single stators 2 a are used as theU-phase stator 2 u, the V-phase stator 2 v and the W-phase stator 2 wand they are stacked on one another in the axial direction to form thethree-phase stator 2.

More specifically, the U-phase stator 2 u, the V-phase stator 2 v andthe W-phase stator 2 w are stacked on one another in this order.

At this time, as shown in FIG. 13, the three-phase stator 2 includingthe U-phase stator 2 u, the V-phase stator 2 v and the W-phase stator 2w is configured by stacking the U-phase stator 2 u, the V-phase stator 2v and the W-phase stator 2 w on one another such that the stators 2 u,2V and 2W are displaced from one another by 5° in mechanical angle (60°in electrical angle).

More specifically, the V-phase stator 2 v is fixed to the motor housingsuch that the V-phase stator 2 v is displaced by 5° in mechanical angle(60° in electrical angle) from the U-phase stator 2 u around the centeraxis O in the clockwise direction as viewed from the U-phase stator 2 u.The W-phase stator 2 w is fixed to the motor housing such that theW-phase stator 2 w is displaced by 5° in mechanical angle (60° inelectrical angle) from the V-phase stator 2 v around the center axis Oin the clockwise direction as viewed from the V-phase stator 2 v.

As shown in FIG. 14, U-phase AC current Iu (single phase current) of thethree-phase AC power source flows through the first to fourth annularwindings 101 to 104 of the U-phase stator 2 u. V-phase AC current Iv(single phase current) of the three-phase AC power source flows throughthe first to fourth annular windings 101 to 104 of the V-phase stator 2v. W-phase AC current Iw (single phase current) of the three-phase ACpower source flows through the first to fourth annular windings 101 to104 of the W-phase stator 2 w.

Next, operations of the brushless motor M of the first embodiment havingthe above-described configuration will be described.

Three-phase AC power source is applied to the three-phase stator 2. Thatis, U-phase AC current Iu flows through the first to fourth annularwindings 101 to 104 of the U-phase stator 2 u, V-phase AC currentlyflows through the first to fourth annular windings 101 to 104 of theV-phase stator 2 v, and W-phase AC current Iw flows through the first tofourth annular windings 101 to 104 of the W-phase stator 2 w. Accordingto this, rotating field is generated in the three-phase stator 2, andthe three-phase rotor 1 is rotated and driven.

At this time, the three-phase stator 2 is formed into the three-partstructure of the U-phase stator 2 u, V-phase stator 2 v and W-phasestator 2 w in accordance with the three-phase AC power source. Inaccordance with this, the three-phase rotor 1 is also formed into thethree-part structure of the U-phase rotor 1 u, the V-phase rotor 1 v andthe W-phase rotor 1 w. According to this, in the stators and rotors ofthe respective phases, the stators which face along the axial directioncan receive magnetic flux of the first to fourth field magnets 51 to 54,and output can be increased.

In the rotors (single rotor 1 a) of the respective phases, the first tofourth four rotor cores 10, 20, 30 and 40 are stacked on one another inthe axial direction in this order such that the first to fourth fieldmagnets 51 to 54 are respectively interposed therebetween. By the firstto fourth field magnets 51 to 54, the first rotor-side claw-shapedmagnetic poles 13 of the first rotor core 10 and the third rotor-sideclaw-shaped magnetic poles 33 of the third rotor core 30 are made northpoles, and the second rotor-side claw-shaped magnetic poles 23 of thesecond rotor core 20 and the fourth rotor-side claw-shaped magneticpoles 43 of the fourth rotor core 40 are made south poles.

The tip end surfaces 16 of the first rotor-side claw-shaped magneticpoles 13 and the tip end surfaces 36 of the third rotor-side claw-shapedmagnetic pole 33 are made to abut against each other in the axialdirection, and the tip end surfaces 26 of the second rotor-sideclaw-shaped magnetic pole 23 and the tip end surfaces 46 of the fourthrotor-side claw-shaped magnetic pole 43 are made to abut against eachother in the axial direction.

As a result, variation in a magnetic flux density between base ends andtip ends of the first rotor-side claw-shaped magnetic poles 13 (thirdrotor-side claw-shaped magnetic poles 33) becomes small as compared witha case where the tip end surfaces 16 of the first rotor-side claw-shapedmagnetic poles 13 and the tip end surfaces 36 of the third rotor-sideclaw-shaped magnetic poles 33 are separated from each other. Similarly,variation in a magnetic flux density between base ends and tip ends ofthe second rotor-side claw-shaped magnetic poles 23 (fourth rotor-sideclaw-shaped magnetic poles 43) becomes small as compared with a casewhere the tip end surfaces 26 of the second rotor-side claw-shapedmagnetic poles 23 and the tip end surfaces 46 of the fourth rotor-sideclaw-shaped magnetic poles 43 are separated from each other.

That is, when both the tip end surfaces 16 and 36 of the first and thirdrotor-side claw-shaped magnetic poles 13 and 33 are separated from eachother and opened, the a magnetic flux density of the base ends of thefirst and third rotor-side claw-shaped magnetic poles 13 and 33 is high(dense), and magnetic resistance of the opened portions between the tipends of the first and third rotor-side claw-shaped magnetic poles 13 and33 becomes large, and the magnetic flux density of these portionsbecomes low (sparse).

In other words, a magnetic flux density distribution of the north poleslargely varies in the axial direction, and an uneven magnetic fluxdensity distribution in the axial direction is given to the first andthird stator-side claw-shaped magnetic poles 64 and 84 of the singlestator 2 a.

Similarly, when both the tip end surfaces 26 and 46 of the second andfourth rotor-side claw-shaped magnetic poles 23 and 43 are separatedfrom each other and opened, the magnetic flux density of the base endsof the second and fourth rotor-side claw-shaped magnetic poles 23 and 43is high, and magnetic resistance of the opened portions between the tipends of the second and fourth rotor-side claw-shaped magnetic poles 23and 43 becomes large, and the magnetic flux density of these portionsbecomes low.

In other words, the magnetic flux density distribution of south poleslargely varies in the axial direction, and an uneven magnetic fluxdensity distribution in the axial direction is given to the second andfourth stator-side claw-shaped magnetic poles 74 and 94 of the singlestator 2 a.

On the other hand, since both the tip end surfaces 16 and 36 of thefirst and third rotor-side claw-shaped magnetic poles 13 and 33 abutagainst each other, magnetic resistance between the tip ends of thefirst and third rotor-side claw-shaped magnetic poles 13 and 33 becomessmall, and variation in the magnetic flux density between the base endsand the tip ends of the first and third rotor-side claw-shaped magneticpoles 13 and 33 becomes small. As a result, variation in the magneticflux density distribution of the north poles becomes small in the axialdirection, and a uniform magnetic flux density distribution in the axialdirection is given to the first and third stator-side claw-shapedmagnetic poles 64 and 84 of the single stator 2 a.

Similarly, since both the tip end surfaces 26 and 46 of the second andfourth rotor-side claw-shaped magnetic poles 23 and 43 abut against eachother, magnetic resistance between the tip ends of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 becomes small, andvariation in the magnetic flux density between the base ends and the tipends of the second and fourth rotor-side claw-shaped magnetic poles 23and 43 becomes small. As a result, variation in the magnetic fluxdensity distribution of the south poles becomes small in the axialdirection, and a uniform magnetic flux density distribution in the axialdirection is given to the second and fourth stator-side claw-shapedmagnetic poles 74 and 94 of the single stator 2 a.

According to this, the rotors of the respective phases can individuallygive magnetic flux having a uniform magnetic flux density distributionin the axial direction to the opposed stators, and output can further beenhanced.

In the stators (single stators 2 a) of the respective phases, the firstto fourth four stator cores 60, 70, 80 and 90 are stacked on one anotherin the axial direction in this order such that the first to fourthannular windings 101 to 104 are respectively interposed therebetween.

The tip end surfaces 67 of the first stator-side claw-shaped magneticpoles 64 and the tip end surfaces 87 of the third stator-sideclaw-shaped magnetic poles 84 are made to abut against each other in theaxial direction, and the tip end surfaces 77 of the second stator-sideclaw-shaped magnetic poles 74 and the tip end surfaces 97 of the fourthstator-side claw-shaped magnetic poles 94 are made to abut against eachother in the axial direction.

As a result, variation in a magnetic flux density between the base endsand the tip ends of the first stator-side claw-shaped magnetic poles 64(third stator-side claw-shaped magnetic poles 84) becomes small ascompared with a case where the tip end surfaces 67 of the firststator-side claw-shaped magnetic poles 64 and the tip end surfaces 87 ofthe third stator-side claw-shaped magnetic poles 84 are separated fromeach other. Similarly, variation in a magnetic flux density between thebase ends and the tip ends of the second stator-side claw-shapedmagnetic poles 74 (fourth stator-side claw-shaped magnetic poles 94)becomes small as compared with a case where the tip end surfaces 77 ofthe second stator-side claw-shaped magnetic pole 74 and the tip endsurfaces 97 of the fourth stator-side claw-shaped magnetic poles 94 areseparated from each other.

That is, when both the tip end surfaces 67 and 87 of the first and thirdstator-side claw-shaped magnetic poles 64 and 84 are separated from eachother and opened, the magnetic flux density of the base ends of thefirst and third stator-side claw-shaped magnetic poles 64 and 84 ishigh, and magnetic resistance of the opened portions between the tipends of the first and third stator-side claw-shaped magnetic poles 64and 84 becomes large, and the magnetic flux density of these portionsbecomes low.

In other words, the magnetic flux density distribution (strengthdistribution of rotating field in axial direction) in the axialdirection largely varies, and an uneven magnetic flux densitydistribution in the axial direction is given to the first and thirdrotor-side claw-shaped magnetic poles 13 and 33 of the single rotor 1 a.

Similarly, when both the tip end surfaces 77 and 97 of the second andfourth stator-side claw-shaped magnetic poles 74 and 94 are separatedfrom each other and opened, the magnetic flux density of the base endsof the second and fourth stator-side claw-shaped magnetic poles 74 and94 is high, and magnetic resistance of the opened portions between thetip ends of the second and fourth stator-side claw-shaped magnetic poles74 and 94 becomes large, and the magnetic flux density of these portionsbecomes low.

In other words, the magnetic flux density distribution (strengthdistribution of rotating field in axial direction) in the axialdirection largely varies in the axial direction, and an uneven magneticflux density distribution in the axial direction is given to the secondand fourth rotor-side claw-shaped magnetic poles 23 and 43 of the singlerotor 1 a.

On the other hand, since both the tip end surfaces 16 and 36 of thefirst and third stator-side claw-shaped magnetic poles 64 and 84 abutagainst each other, magnetic resistance between the tip ends of thefirst and third stator-side claw-shaped magnetic poles 64 and 84 becomessmall, and variation in the magnetic flux density between the base endsand the tip ends of the first and third stator-side claw-shaped magneticpoles 64 and 84 becomes small. As a result, variation in the magneticflux density distribution in the axial direction (strength distributionof rotating field in axial direction) becomes small, and a uniformmagnetic flux density distribution in the axial direction is given tothe first and third rotor-side claw-shaped magnetic poles 13 and 33 ofthe single rotor 1 a.

Similarly, since both the tip end surfaces 77 and 97 of the second andfourth stator-side claw-shaped magnetic poles 74 and 94 abut againsteach other, magnetic resistance between the tip ends of the second andfourth stator-side claw-shaped magnetic poles 74 and 94 becomes small,and variation in the magnetic flux density between the base ends and thetip ends of the second and fourth stator-side claw-shaped magnetic poles74 and 94 becomes small. As a result, variation in the magnetic fluxdensity distribution in the axial direction (strength distribution ofrotating field in axial direction) becomes small, and a uniform magneticflux density distribution in the axial direction is given to the secondand fourth rotor-side claw-shaped magnetic poles 23 and 43 of the singlerotor 1 a.

Further, a variation cycle of a magnetic flux density of the first andthird stator-side claw-shaped magnetic poles 64 and 84 and a variationcycle of a magnetic flux density of the second and fourth stator-sideclaw-shaped magnetic poles 74 and 94 are deviated from each other by180° in phase.

According to this, the stators of the respective phases can individuallygive magnetic flux having a uniform magnetic flux density distributionin the axial direction to the opposed rotors, and output can beincreased.

The U-phase stator 2 u, the V-phase stator 2 v and the W-phase stator 2w of the three-phase stator 2 are displaced from one another in theclockwise direction by 5° in mechanical angle (60° in electrical anglein clockwise direction), whereas the U-phase rotor 1 u, the V-phaserotor 1 v and the W-phase rotor 1 w of the three-phase rotor 1 aredisplaced from one another in the counter clockwise direction by 5° inmechanical angle (60° in electrical angle in counterclockwisedirection). That is, between the U-phase rotor 1 u, the V-phase rotor 1v and the W-phase rotor 1 w which face the U-phase stator 2 u, theV-phase stator 2 v and the W-phase stator 2 w, displacements in thecircumferential direction incline in mutually opposite directions at thesurfaces facing each other.

According to this, sets of the first and third rotor-side claw-shapedmagnetic poles 13 and 33 in each phase and sets of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 in each phase can bemade to appropriately follow the switching of magnetic flux of sets ofthe first and third stator-side claw-shaped magnetic poles 64 and 84 ineach phase and sets of the second and fourth stator-side claw-shapedmagnetic poles 74 and 94 in each phase due to AC currents Iu, Iv and Iwin each phase flowing through the first to fourth annular windings 101to 104 in each phase. As a result, it is possible to realize excellentrotation of the three-phase rotor 1.

Next, advantages of the first embodiment will be described below.

(1) According to the first embodiment, the three-phase rotor 1 is formedinto the three-part structure including the U-phase rotor 1 u, theV-phase rotor 1 v and the W-phase rotor 1 w and correspondingly, thethree-phase stator 2 is also formed into the three-part structureincluding the U-phase stator 2 u, the V-phase stator 2 v and the W-phasestator 2 w. Three-phase AC power source is applied to the three-phasestator 2. In the stators and the rotors of the respective phases, thestators which face along the axial direction can individually receivemagnetic fluxes of the first to fourth field magnets 51 to 54.Therefore, output of the brushless motor M can be increased.

Further, the displacement direction of the three-phase (three-part)rotors 1 u, 1 v and 1 w in the circumferential direction and thedisplacement direction of the three-phase (three-part) stators 2 u, 2 vand 2 w in the circumferential direction are opposite from each other.Therefore, it is possible to realize excellent rotation of thethree-phase rotor 1.

(2) According to the first embodiment, the single rotor 1 a is formed bystacking the first to fourth rotor cores 10, 20, 30 and 40 in the axialdirection in this order such that the first to fourth field magnets 51to 54 are respectively interposed therebetween. The tip end surfaces 16of the first rotor-side claw-shaped magnetic poles 13 and the tip endsurfaces 36 of the third rotor-side claw-shaped magnetic poles 33 aremade to abut against each other in the axial direction, and the tip endsurfaces 26 of the second rotor-side claw-shaped magnetic poles 23 andthe tip end surfaces 46 of the fourth rotor-side claw-shaped magneticpoles 43 are made to abut against each other in the axial direction.

Therefore, the first and third rotor-side claw-shaped magnetic poles 13and 33 of the single rotor 1 a having the same poles can give magneticfluxes having a magnetic flux density distribution which is uniform inthe axial direction to the first and third stator-side claw-shapedmagnetic poles 64 and 84 of the single stator 2 a. Similarly, the secondand fourth rotor-side claw-shaped magnetic poles 23 and 43 of the singlerotor 1 a having the same poles can give magnetic fluxes having auniform magnetic flux density distribution in the axial direction to thesecond and fourth stator-side claw-shaped magnetic poles 74 and 94 ofthe single stator 2 a.

According to this, the rotors of the respective phases can give magneticfluxes of a magnetic flux density distribution which is uniform in theaxial direction to the opposed stators, and output can be increased.

(3) According to the first embodiment, the single stator 2 a is formedby stacking the first to fourth stator cores 60, 70, 80 and 90 in theaxial direction in this order such that the first to fourth annularwindings 101 to 104 are respectively interposed therebetween.

The tip end surfaces 67 of the first stator-side claw-shaped magneticpoles 64 and the tip end surfaces 87 of the third stator-sideclaw-shaped magnetic poles 84 are made to abut against each other in theaxial direction, and the tip end surfaces 77 of the second stator-sideclaw-shaped magnetic poles 74 and the tip end surfaces 97 of the fourthstator-side claw-shaped magnetic poles 94 are made to abut against eachother in the axial direction.

Therefore, the first and third stator-side claw-shaped magnetic poles 64and 84 of the single stator 2 a can give magnetic fluxes having amagnetic flux density distribution which is uniform in the axialdirection to the first and third rotor-side claw-shaped magnetic poles13 and 33 of the single rotor 1 a. Similarly, the second and fourthstator-side claw-shaped magnetic poles 74 and 94 of the single stator 2a can give magnetic fluxes having a magnetic flux density distributionwhich is uniform in the axial direction to the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 of the single rotor 1 a.

As a result, the stators of the respective phases can give magneticfluxes (rotating field) of a magnetic flux density distribution which isuniform in the axial direction to the opposed rotors, and output canfurther be increased.

(4) According to the first embodiment, the single rotor 1 a includes thefirst to fourth rotor cores 10, 20, 30 and 40 and the first to fourthfield magnets 51 to 54.

When the third and fourth rotor cores 30 and 40 are inverted in theaxial direction with respect to the first and second rotor cores 10 and20, shapes of the third and fourth rotor cores 30 and 40 become the sameas those of the first and second rotor cores 10 and 20.

When the second and third field magnets 52 and 53 are inverted in theaxial direction with respect to the first and fourth field magnets 51and 54, the second and third field magnets 52 and 53 have the samemagnetizing direction and the same features as those of the first andfourth field magnets 51 and 54.

Therefore, the single rotor 1 a (three-phase rotor 1) can be formed bytwo types of constituent parts, management of parts becomes easy, andthe assembling steps also becomes easy.

(5) According to the first embodiment, the single stator 2 a includesthe first to fourth stator cores 60, 70, 80 and 90 and the first tofourth annular windings 101 to 104.

When the third and fourth stator cores 80 and 90 are inverted in theaxial direction with respect to the first and second stator cores 60 and70, features of the third and fourth stator cores 80 and 90 become thesame as those of the first and second stator cores 60 and 70.

When the second and third annular winding 102 and 103 are inverted inthe axial direction with respect to the first and fourth annularwindings 101 and 104, the second and third annular winding 102 and 103have the same winding direction and the same features as those of thefirst and fourth annular windings 101 and 104.

Therefore, the single stator 2 a (three-phase stator 2) can be formed bytwo types of constituent parts, management of parts becomes easy, andthe assembling steps also becomes easy.

From these facts, the single motor Ma (brushless motor M) can be formedby four types of constituent parts, management of parts becomes easy,and the assembling steps also become easy.

Second Embodiment

A second embodiment of the motor will be described in accordance withFIGS. 15 to 21.

The second embodiment is characterized in that tip end surfaces 16 offirst rotor-side claw-shaped magnetic poles 13 and tip end surfaces 36of third rotor-side claw-shaped magnetic poles 33 are not made to abutagainst each other but are closely opposed to each other, and tip endsurfaces 26 of second rotor-side claw-shaped magnetic poles 23 and tipend surfaces 46 of fourth rotor-side claw-shaped magnetic poles 43 arenot made to abut against each other but are closely opposed to eachother.

The second embodiment is also characterized in that tip end surfaces 67of first stator-side claw-shaped magnetic poles 64 and tip end surfaces87 of third stator-side claw-shaped magnetic poles 84 are not made toabut against each other but are closely opposed to each other, and tipend surfaces 77 of second stator-side claw-shaped magnetic poles 74 andtip end surfaces 97 of fourth stator-side claw-shaped magnetic pole 94are not made to abut against each other but are closely opposed to eachother.

Therefore, in the second embodiment, characteristic portions will bedescribed in detail, the same reference numerals as those of the firstembodiment are allocated to members of common portions, and detaileddescription thereof will be omitted for the sake of convenience ofdescription.

As shown in FIG. 15, each of single motors Ma of respective phasesconfiguring a three-phase brushless motor M includes a single rotor 1 aand a single stator 2 a.

(Single Rotor 1 a)

As shown in FIG. 16A, thicknesses of the first to fourth field magnets51 to 54 are the same as those of the first embodiment. On the otherhand, lengths of first to fourth rotor-side claw-shaped magnetic poles13, 23, 33 and 43 in the axial direction are less than three times ofthicknesses (lengths in axial direction of rotor) of first to fourthrotor core bases 11, 21, 31 and 41.

Therefore, as shown in FIGS. 15 and 16A, the tip end surfaces 16 of thefirst rotor-side claw-shaped magnetic poles 13 and the tip end surfaces36 of the third rotor-side claw-shaped magnetic poles 33 are closelyopposed to each other in the axial direction, i.e., opposed to eachother in the axial direction such that gaps G of a certain distance areformed therebetween. Similarly, the tip end surfaces 26 of the secondrotor-side claw-shaped magnetic poles 23 and the tip end surfaces 46 ofthe fourth rotor-side claw-shaped magnetic poles 43 are opposed to eachother in the axial direction, i.e., opposed to each other in the axialdirection such that gaps G of a certain distance are formedtherebetween.

That is, the single rotor 1 a of the second embodiment is of a Lundelltype structure having the gaps G between the tip end surfaces 16 and 36of the first and third rotor-side claw-shaped magnetic poles 13 and 33,and between the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43.

As shown in FIGS. 17 and 18, the single rotors 1 a are used as a U-phaserotor 1 u, a V-phase rotor 1 v and a W-phase rotor 1 w and these rotorsare stacked on one another in the axial direction to form the rotor 1 ofthe three-phase brushless motor M as in the first embodiment.

At this time, as in the first embodiment, the U-phase rotor 1 u and theW-phase rotor 1 w are placed such that placement directions of first tofourth rotor cores 10, 20, 30 and 40 (first to fourth field magnets 51to 54) become the same. On the other hand, the V-phase rotor 1 v whichis stacked between the U-phase rotor 1 u and the W-phase rotor 1 w isplaced such that placement directions of the first to fourth rotor cores10, 20, 30 and 40 (first to fourth field magnets 51 to 54) of theV-phase rotor 1 v become opposite from the placement directions of thefirst to fourth rotor cores 10, 20, 30 and 40 (first to fourth fieldmagnets 51 to 54) of the U-phase rotor 1 u and the W-phase rotor 1 w.

Further, as shown in FIG. 18, the three-phase rotor 1 including theU-phase rotor 1 u, the V-phase rotor 1 v and the W-phase rotor 1 w isconfigured by stacking the U-phase rotor 1 u, the V-phase rotor 1 v andthe W-phase rotor 1 w on one another such that the rotors 1 u, 1 v and 1w are displaced from one another by 5° in mechanical angle (60° inelectrical angle) as in the first embodiment.

(Single Stator 2 a)

As shown in FIG. 16B, coil lengths (lengths in axial direction) of firstto fourth annular windings 101 to 104 are the same as those of the firstembodiment.

On the other hand, lengths of first to fourth stator-side claw-shapedmagnetic poles 64, 74, 84 and 94 in the axial direction are less thanthree times of thicknesses (lengths in axial direction) of first tofourth stator core bases 61, 71, 81 and 91.

Therefore, as shown in FIGS. 15 and 16B, the tip end surfaces 67 of thefirst stator-side claw-shaped magnetic poles 64 and the tip end surfaces87 of the third stator-side claw-shaped magnetic poles 84 are closelyopposed to each other in the axial direction, i.e., opposed to eachother in the axial direction such that gaps G of a certain distance areformed therebetween. Similarly, the tip end surfaces 77 of the secondstator-side claw-shaped magnetic poles 74 and the tip end surfaces 97 ofthe fourth stator-side claw-shaped magnetic poles 94 are closely opposedto each other in the axial direction, i.e., opposed to each other in theaxial direction such that gaps G of a certain distance are formedtherebetween.

That is, the single rotor 2 a of the second embodiment is of a Lundelltype structure having the gaps G between the tip end surfaces 67 and 87of the first and third stator-side claw-shaped magnetic poles 64 and 84,and between the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94.

As shown in FIGS. 19 and 20, the single stators 2 a are used as aU-phase stator 2 u, a V-phase stator 2 v and a W-phase stator 2 w andthe stators 2 u, 2 v and 2 w are stacked on one another in the axialdirection to form the stator 2 of the three-phase brushless motor M asin the first embodiment.

At this time, as in the first embodiment, the three-phase stator 2including the U-phase stator 2 u, the V-phase stator 2 v and the W-phasestator 2 w is configured by stacking the U-phase stator 2 u, the V-phasestator 2 v and the W-phase stator 2 w on one another such that thesestators 2 u, 2 v and 2 w are displaced from one another by 5° inmechanical angle (60° in electrical angle).

U-phase AC current Iu of a three-phase AC power source flows through thefirst to fourth annular windings 101 to 104 of the U-phase stator 2 u.V-phase AC current Iv of the three-phase AC power source flows throughthe first to fourth annular windings 101 to 104 of the V-phase stator 2v. Further, W-phase AC current Iw of the three-phase AC power sourceflows through the first to fourth annular windings 101 to 104 of theW-phase stator 2 w.

Next, operations of the brushless motor M of the second embodimenthaving the above-described configuration will be described.

Now, three-phase AC power source is applied to the three-phase stator 2.That is, U-phase AC current Iu flows through the first to fourth annularwindings 101 to 104 of the U-phase stator 2 u, V-phase AC current Ivflows through the first to fourth annular windings 101 to 104 of theV-phase stator 2 v, and W-phase AC current Iw flows through the first tofourth annular windings 101 to 104 of the W-phase stator 2 w. Accordingto this, rotating field is generated in the three-phase stator 2, andthe three-phase rotor 1 is rotated and driven.

At this time, the three-phase stator 2 is formed into the three-partstructure having the U-phase stator 2 u, the V-phase stator 2 v and theW-phase stator 2 w in accordance with the three-phase AC power source.In accordance with this, the three-phase rotor 1 is also formed into thethree-part structure having the U-phase rotor 1 u, the V-phase rotor 1 vand the W-phase rotor 1 w. According to this, in the stators and therotors of the respective phases, the stators which are opposed to eachother along the axial direction can individually receive magnetic fluxesof the first to fourth field magnets 51 to 54, and output can beincreased.

In the rotors (single rotors 1 a) of the respective phases, the first tofourth four rotor cores 10, 20, 30 and 40 are stacked on one another inthe axial direction in this order such that the first to fourth fieldmagnets 51 to 54 are respectively interposed therebetween. By the firstto fourth field magnets 51 to 54, the first rotor-side claw-shapedmagnetic poles 13 of the first rotor core 10 and the third rotor-sideclaw-shaped magnetic poles 33 of the third rotor core 30 are made asnorth poles, and the second rotor-side claw-shaped magnetic poles 23 ofthe second rotor core 20 and the fourth rotor-side claw-shaped magneticpoles 43 of the fourth rotor core 40 are made as south poles.

At this time, a magnetic flux density of the second rotor-sideclaw-shaped magnetic poles 23 is determined based on three field magnetsincluding the first, second and third field magnets 51, 52 and 53. Amagnetic flux density of the third rotor-side claw-shaped magnetic poles33 is determined based on the three field magnets including the second,third and fourth field magnets 52, 53 and 54.

On the other hand, a magnetic flux density of the first rotor-sideclaw-shaped magnetic poles 13 is determined based on the one first fieldmagnet 51. Similarly, a magnetic flux density of the fourth rotor-sideclaw-shaped magnetic poles 43 is determined based on the one fourthfield magnet 54.

As a result, a difference in generated magnetic fluxes of the mutuallyopposed first rotor-side claw-shaped magnetic poles 13 and thirdrotor-side claw-shaped magnetic poles 33 becomes large. Therefore, whenthe tip end surfaces 16 and 36 are in abutment against each other,magnetic fluxes reversely flow between the first rotor-side claw-shapedmagnetic poles 13 and the third rotor-side claw-shaped magnetic poles33. According to this, a magnetic flux density of north poles becomessmall as a whole, and north poles of a small magnetic flux density aregiven to the first and third stator-side claw-shaped magnetic poles 64and 84 of the opposed stators 2 a.

Similarly, a difference in generated magnetic fluxes of the secondrotor-side claw-shaped magnetic poles 23 and fourth rotor-sideclaw-shaped magnetic poles 43 also becomes large. Therefore, when thetip end surfaces 26 and 46 are in abutment against each other, magneticfluxes reversely flow between the second rotor-side claw-shaped magneticpoles 23 and the fourth rotor-side claw-shaped magnetic poles 43.According to this, a magnetic flux density of south poles becomes smallas a whole, and south poles of a small magnetic flux density are givento the second and fourth stator-side claw-shaped magnetic poles 74 and94 of the opposed stators 2 a.

On the other hand, the tip end surfaces 16 and 36 of the first and thirdrotor-side claw-shaped magnetic poles 13 and 33 are closely opposed toeach other in the axial direction, and magnetic resistance between thetip end surfaces 16 and 36 is increased. As a result, reverse flow ofmagnetic fluxes between the first rotor-side claw-shaped magnetic poles13 and the third rotor-side claw-shaped magnetic poles 33 based on adifference in generated magnetic fluxes is suppressed, and a magneticflux density of north poles is increased as a whole.

Similarly, the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 are closely opposed toeach other in the axial direction, magnetic resistance between the tipend surfaces 26 and 46 is increased, reverse flow of magnetic fluxesbetween the second rotor-side claw-shaped magnetic poles 23 and thefourth rotor-side claw-shaped magnetic poles 43 based on a difference ingenerated magnetic fluxes is suppressed, and a magnetic flux density ofsouth poles is increased as a whole.

According to this, the rotors of the respective phases can individuallygive magnetic poles having a large magnetic flux density to the opposedstators, and output can further be increased.

In the stators (single stators 2 a) of the respective phases, the firstto fourth four stator cores 60, 70, 80 and 90 are stacked on one anotherin the axial direction in this order such that the first to fourthannular windings 101 to 104 are respectively interposed therebetween.

At this time, a magnetic flux density of rotating field of the secondstator-side claw-shaped magnetic poles 74 is determined based on threeannular windings, i.e., the first, second and third annular windings101, 102 and 103. A magnetic flux density of rotating field of the thirdstator-side claw-shaped magnetic poles 84 is determined based on threeannular windings, i.e., the second, third and fourth annular windings102, 103 and 104.

On the other hand, a magnetic flux density of rotating field of thefirst stator-side claw-shaped magnetic poles 64 is determined based onthe one first annular winding 101. Similarly, a magnetic flux density ofrotating field of the fourth stator-side claw-shaped magnetic poles 94is determined based on the one first annular winding 104.

As a result, a difference in generated magnetic fluxes of rotating fieldbetween the mutually opposed first stator-side claw-shaped magneticpoles 64 and third stator-side claw-shaped magnetic poles 84 becomeslarge. Therefore, when the tip end surfaces 67 and 87 are in abutmentagainst each other, magnetic fluxes reversely flow between the firststator-side claw-shaped magnetic poles 64 and the third stator-sideclaw-shaped magnetic poles 84. According to this, a magnetic fluxdensity of rotating field becomes small as a whole, and rotating fieldwhich becomes small is given to the first and third rotor-sideclaw-shaped magnetic poles 13 and 33 of the opposed rotors 1 a.

Similarly, a difference in generated magnetic fluxes of rotating fieldbecomes large also in the second stator-side claw-shaped magnetic poles74 and the fourth stator-side claw-shaped magnetic poles 94. Therefore,when the tip end surfaces 77 and 97 are in abutment against each other,magnetic fluxes reversely flow between the first stator-side claw-shapedmagnetic poles 64 and the third stator-side claw-shaped magnetic poles84. According to this, a magnetic flux density of rotating field becomessmall as a whole, and rotating field which becomes small is given to thesecond and fourth rotor-side claw-shaped magnetic poles 23 and 43 of theopposed rotors 1 a.

On the other hand, the tip end surfaces 67 and 87 of the first and thirdstator-side claw-shaped magnetic poles 64 and 84 are closely opposed toand separated from each other in the axial direction, and magneticresistance between the tip end surfaces 67 and 87 is increased. As aresult, reverse flow of magnetic fluxes between the first stator-sideclaw-shaped magnetic pole 64 and the third stator-side claw-shapedmagnetic pole 84 based on a difference in generated magnetic fluxes issuppressed, and a magnetic flux density of rotating field is increasedas a whole.

Similarly, the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94 are closely opposed toeach other in the axial direction, magnetic resistance between the tipend surfaces 77 and 97 is increased, reverse flow of magnetic fluxesbetween the second stator-side claw-shaped magnetic pole 74 and thefourth stator-side claw-shaped magnetic pole 94 based on a difference ingenerated magnetic fluxes is suppressed, and a magnetic flux density ofrotating field is increased as a whole.

According to this, the stators of the respective phases can individuallygive rotating field having a large magnetic flux density to the opposedrotors, and output can further be increased.

FIG. 21 shows characteristic curves for comparison between torquecharacteristics of brushless motors M of the first embodiment and thesecond embodiment.

A characteristic curve L1 shows torque characteristics of the brushlessmotor M of the first embodiment, and a characteristic curve L2 showstorque characteristics of the brushless motor M of the secondembodiment. Experiment conditions of the two embodiments are the sameexcept a condition as to whether opposed tip end surfaces of the rotorand opposed tip end surfaces of the stator abut against or separate fromeach other.

From a result of this experiment, it can be understood that a brushlessmotor M of higher torque is obtained based on the above-describedreasons.

As described above in detail, the second embodiment has the followingeffects in addition to the advantages of the first embodiment.

(6) According to the second embodiment, the tip end surfaces 16 and 36of the first and third rotor-side claw-shaped magnetic poles 13 and 33are closely opposed to each other in the axial direction, reverse flowof magnetic fluxes between the first rotor-side claw-shaped magneticpole 13 and the third rotor-side claw-shaped magnetic pole 33 based on adifference in generated magnetic fluxes is suppressed, and a magneticflux density of north poles is increased as a whole.

Similarly, the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 are closely opposed toeach other in the axial direction, reverse flow of magnetic fluxesbetween the second rotor-side claw-shaped magnetic pole 23 and thefourth rotor-side claw-shaped magnetic pole 43 based on a difference ingenerated magnetic fluxes is suppressed, and a magnetic flux density ofsouth poles is increased as a whole.

According to this, the rotors of the respective phases can individuallygive magnetic poles having a large magnetic flux density to the opposedstators, and output can further be increased.

(7) According to the second embodiment, the tip end surfaces 67 and 87of the first and third stator-side claw-shaped magnetic poles 64 and 84are closely opposed to each other in the axial direction, reverse flowof magnetic fluxes between the first stator-side claw-shaped magneticpole 64 and the third stator-side claw-shaped magnetic pole 84 based ona difference in generated magnetic fluxes is suppressed, and a magneticflux density of rotating field is increased as a whole.

Similarly, the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94 are closely opposed toeach other in the axial direction, reverse flow of magnetic fluxesbetween the second stator-side claw-shaped magnetic pole 74 and thefourth stator-side claw-shaped magnetic pole 94 based on a difference ingenerated magnetic fluxes is suppressed, and a magnetic flux density ofrotating field is increased as a whole.

According to this, the stators of the respective phases can individuallygive rotating field having a large magnetic flux density to the opposedrotors, and output can further be increased.

(8) According to the second embodiment, since the tip end surfaces 16and 36 of the first and third rotor-side claw-shaped magnetic poles 13and 33 are closely opposed to each other in the axial direction,variation in a magnetic flux density distribution can be reduced in theaxial direction.

Similarly, since the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 are closely opposed toeach other in the axial direction, variation in a magnetic flux densitydistribution can be reduced in the axial direction.

According to this, the rotors of the respective phases can individuallygive magnetic fluxes of a magnetic flux density distribution havingsmall axial variation to the opposed stators, and output can further beincreased.

(9) According to the second embodiment, since the tip end surfaces 67and 87 of the first and third stator-side claw-shaped magnetic poles 64and 84 are closely opposed to each other in the axial direction,variation in a magnetic flux density distribution can be reduced in theaxial direction.

Similarly, since the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94 are closely opposed toeach other in the axial direction, variation in a magnetic flux densitydistribution can be reduced in the axial direction.

As a result, the stators of the respective phases can individually givemagnetic fluxes (rotating field) of a magnetic flux density distributionhaving small axial variation to the opposed rotors, and output canfurther be increased.

Third Embodiment

A third embodiment of the motor will be described in accordance withFIGS. 22 to 28.

The third embodiment is different from the first embodiment, and ischaracterized in that one field magnet is placed between a second rotorcore 20 and a third rotor core 30, and one annular winding is placedbetween a second stator core 70 and a third stator core 80.

Therefore, in the third embodiment, characteristic portions will bedescribed in detail, the same reference numerals as those of the firstembodiment are allocated to members of common portions, and detaileddescription thereof will be omitted for the sake of convenience ofdescription.

As shown in FIG. 22, each of single motors Ma of respective phasesconfiguring a three-phase brushless motor M includes a single rotor 1 aand a single stator 2 a.

(Single Rotor 1 a)

As shown in FIG. 23A, one field magnet (central field magnet 52A,hereinafter) is placed between the second rotor core 20 (second rotorcore base 21) and the third rotor core 30 (third rotor core base 31).The central field magnet 52A has the same shape and the same functionand is made of the same material as those of the first field magnet 51and the fourth field magnet 54.

That is, a thickness (length in axial direction of the rotor) of thecentral field magnet 52A is the same as those of the first field magnet51 and the fourth field magnet 54. A diameter of the central fieldmagnet 52A is the same as those of the first field magnet 51 and thefourth field magnet 54. Further, strength of a magnetic force of thecentral field magnet 52A is the same as those of the first field magnet51 and the fourth field magnet 54.

Therefore, since the thickness of the central field magnet 52A is thesame as those of the first and fourth field magnets 51 and 54, adistance between the second and third rotor core bases 21 and 31 is thesame as a distance between first and second rotor core bases 11 and 21and a distance between third and fourth rotor core bases 31 and 41.

The central field magnet 52A is magnetized in the axial direction suchthat a portion thereof closer to the second rotor core 20 becomes southpole, and a portion thereof closer to the third rotor core 30 becomesnorth pole. Therefore, by the central field magnet 52A, secondrotor-side claw-shaped magnetic poles 23 of the second rotor core 20function as south poles (second magnetic poles), and third rotor-sideclaw-shaped magnetic poles 33 of the third rotor core 30 function asnorth poles (first magnetic poles).

Since the central field magnet 52A is placed between the second rotorcore base 21 and the third rotor core base 31, lengths of first tofourth rotor-side claw-shaped magnetic poles 13, 23, 33 and 43 in theaxial direction are made short so that tip end surfaces 16 and 36 andtip end surfaces 26 and 46 abut against each other.

More specifically, a length of each of the first rotor-side claw-shapedmagnetic poles 13 in the axial direction (length between the tip endsurface 16 and a surface of first rotor core base 11 opposite from asurface thereof which faces the second rotor core 20) is 2.5 times of athickness (length in axial direction) of the first rotor core base 11.

A length of each of the second rotor-side claw-shaped magnetic poles 23in the axial direction (length between tip end surface 26 and surface ofsecond rotor core base 21 opposite from surface thereof which is opposedto first rotor core 10) is 2.5 times of a thickness (length in axialdirection) of the second rotor core base 21.

Further, a length of each of the third rotor-side claw-shaped magneticpoles 33 in the axial direction (length between tip end surface 36 andsurface of third rotor core base 31 opposite from surface thereof whichis opposed to fourth rotor core 40) is 2.5 times of a thickness (lengthin axial direction) of the third rotor core base 31.

Further, a length of each of the fourth rotor-side claw-shaped magneticpoles 43 in the axial direction (length between tip end surface 46 andsurface of fourth rotor core base 41 opposite from surface thereof whichis opposed to third rotor core 30) is 2.5 times of a thickness (lengthin axial direction) of the fourth rotor core base 41.

That is, in the single rotor 1 a of the third embodiment, thicknesses ofthe first field magnet 51, the central field magnet 52A and the fourthfield magnet 54 are the same. In other words, a distance between thefirst rotor core base 11 and the second rotor core base 21, a distancebetween the second rotor core base 21 and the third rotor core base 31,and a distance between the third rotor core base 31 and the fourth rotorcore base 41 are the same.

Therefore, as shown in FIG. 23A, the single rotor 1 a of the thirdembodiment is of a Lundell type structure in which the tip end surfaces16 and 36 of the first and third rotor-side claw-shaped magnetic poles13 and 33 whose axial lengths are shortened abut against each other, andthe tip end surfaces 26 and 46 of the second and fourth rotor-sideclaw-shaped magnetic poles 23 and 43 whose axial lengths are shortenedabut against each other.

As shown in FIGS. 24 and 25, the single rotors 1 a are used as a U-phaserotor 1 u, a V-phase rotor 1 v and a W-phase rotor 1 w and these rotors1 u, 1 v and 1 w are stacked on one another in the axial direction toform the rotor 1 of the three-phase brushless motor M as in the firstembodiment.

At this time, like the first embodiment, the U-phase rotor 1 u and theW-phase rotor 1 w are placed such that placement directions of the firstto fourth rotor cores 10, 20, 30 and 40 become the same. On the otherhand, the V-phase rotor 1 v stacked between the U-phase rotor 1 u andthe W-phase rotor 1 w is placed such that placement directions of thefirst to fourth rotor cores 10, 20, 30 and 40 of the V-phase rotor 1 vbecome opposite from the placement directions of the first to fourthrotor cores 10, 20, 30 and 40 of the U-phase rotor 1 u and the W-phaserotor 1 w.

Further, as shown in FIG. 25, the three-phase rotor 1 including theU-phase rotor 1 u, the V-phase rotor 1 v and the W-phase rotor 1 w of isconfigured by stacking the U-phase rotor 1 u, the V-phase rotor 1 v andthe W-phase rotor 1 w on one another such that these rotors 1 u, 1 v and1 w are displaced from one another by 5° in mechanical angle (60° inelectrical angle) as in the first embodiment.

(Single Stator 2 a)

As shown in FIG. 23B, one annular winding (central annular winding 102A,hereinafter) is placed between the second stator core 70 (second statorcore base 71) and the third stator core 80 (third stator core base 81).

The central annular winding 102A is made of the same material and hasthe same shape as those of the first annular winding 101 placed betweenthe first stator core base 61 and the second stator core base 71 and thefourth annular winding 104 placed between the third stator core base 81and the fourth stator core base 91.

That is, a coil length (length in axial direction) of the centralannular winding 102A is the same as those of the first annular winding101 and the fourth annular winding 104. Further, a coil diameter of thecentral annular winding 102A is the same as those of the first annularwinding 101 and the fourth annular winding 104. Further, the windingnumber (number of windings, or winding times) of the central annularwinding 102A is the same as those of the first annular winding 101 andthe fourth annular winding 104.

Therefore, since the coil length of the central annular winding 102A isthe same as those of the first and fourth annular windings 101 and 104,a distance between the second and third stator core bases 71 and 81 isthe same as a distance between the first and second stator core bases 61and 71 and a distance between the third and fourth stator core bases 81and 91.

That is, a second cylindrical wall 72 of the second stator core 70extends toward the third stator core 80 from a surface of the secondstator core base 71 which is opposed to the third stator core 80 alongthe axial direction by a half distance of a thickness of the secondstator core base 71. Similarly, a third cylindrical wall 82 of the thirdstator core 80 extends toward the second stator core 70 from a surfaceof the third stator core base 81 which is opposed to the second statorcore 70 along the axial direction by a half distance of a thickness ofthe third stator core base 81.

According to this, if an annular tip end surface 73 of the secondcylindrical wall 72 and an annular tip end surface 83 of the thirdcylindrical wall 82 abut against each other, a distance between thesecond stator core base 71 and the third stator core base 81 becomes thesame as a distance between the first and second stator core bases 61 and71 and a distance between the third and fourth stator core bases 81 and91.

Since the central annular winding 102A is placed between the second andthird stator core bases 71 and 81, lengths of the first to fourthstator-side claw-shaped magnetic poles 64, 74, 84 and 94 in the axialdirection are formed short so that the tip end surfaces 67 and 87 abutagainst each other and the tip end surfaces 77 and 97 abut against eachother.

More specifically, a length of each of the first stator-side claw-shapedmagnetic poles 64 in the axial direction (length between tip end surface67 and surface of first stator core base 61 opposite from surfacethereof which is opposed to second stator core 70) is 2.5 times of athickness (length in axial direction) of the first stator core base 61.

A length of each of the second stator-side claw-shaped magnetic poles 74in the axial direction (length between tip end surface 77 and surface ofsecond rotor core base 71 opposite from surface thereof which is opposedto first stator core 60) is 2.5 times of a thickness (length in axialdirection) of the second stator core base 71.

Further, a length of each of the third stator-side claw-shaped magneticpoles 84 in the axial direction (length between tip end surface 87 andsurface of third stator core base 81 opposite from surface thereof whichis opposed to fourth stator core 90) is 2.5 times of a thickness (lengthin axial direction) of the third stator core base 81.

Further, a length of each of the fourth stator-side claw-shaped magneticpoles 94 in the axial direction (length between tip end surface 97 andsurface of fourth stator core base 91 opposite from surface thereofwhich is opposed to third stator core 80) is 2.5 times of a thickness(length in axial direction) of the fourth stator core base 91.

That is, in the single stator 2 a of the third embodiment, coil lengthsof the first annular winding 101, the central annular winding 102A andthe fourth annular winding 104 are the same. In other words, a distancebetween the first stator core base 61 and the second stator core base71, a distance between the second stator core base 71 and the thirdstator core base 81, and a distance between the third stator core base81 and the fourth stator core base 91 are the same.

Therefore, as shown in FIG. 23A, the single stator 2 a of the thirdembodiment is of a Lundell type structure in which the tip end surfaces67 and 87 of the first and third stator-side claw-shaped magnetic poles64 and 84 whose axial lengths are shortened abut against each other, andthe tip end surfaces 77 and 97 of the second and fourth stator-sideclaw-shaped magnetic poles 74 and 94 whose axial lengths are shortenedabut against each other.

As shown in FIGS. 26 and 27, the single stators 2 a are used as aU-phase stator 2 u, a V-phase stator 2 v and a W-phase stator 2 w andthese stators 2 u, 2 v and 2 w are stacked on one another in the axialdirection to form the stator 2 of the three-phase brushless motor M asin the first embodiment.

At this time, like the first embodiment, the three-phase stator 2including the U-phase stator 2 u, the V-phase stator 2 v and the W-phasestator 2 w is configured by stacking the U-phase stator 2 u, the V-phasestator 2 v and the W-phase stator 2 w on one another such that thestators 2 u, 2V and 2W are displaced from one another by 5° inmechanical angle (60° in electrical angle).

U-phase AC current Iu of the three-phase AC power source flows throughthe U-phase stator 2 u. V-phase AC current Iv of the three-phase ACpower source flows through the V-phase stator 2 v. W-phase AC current Iwof the three-phase AC power source flows through the W-phase stator 2 w.

Next, operations of the brushless motor M of the third embodiment havingthe above-described configuration will be described.

In the rotor of each of the respective phases, the first to fourth fourrotor cores 10, 20, 30 and 40 are stacked on one another in the axialdirection in this order such that the first, central and fourth fieldmagnets 51, 52A and 54 are respectively interposed therebetween. By thefirst, central and fourth field magnets 51, 52A and 54, the first andthird rotor-side claw-shaped magnetic poles 13 and 33 become northpoles, and the second and fourth rotor-side claw-shaped magnetic poles23 and 43 become south poles.

At this time, a magnetic flux density of the second rotor-sideclaw-shaped magnetic poles 23 is determined based on the two fieldmagnets, i.e., the first field magnet 51 and the central field magnet52A. A magnetic flux density of the third rotor-side claw-shapedmagnetic poles 33 is determined based on the two field magnets, i.e.,the central field magnet 52A and the fourth field magnet 54.

On the other hand, a magnetic flux density of the first rotor-sideclaw-shaped magnetic poles 13 is determined based on the one first fieldmagnet 51. Similarly, a magnetic flux density of the fourth rotor-sideclaw-shaped magnetic poles 43 is determined based on the one fourthfield magnet 54.

As a result, in the mutually opposed first rotor-side claw-shapedmagnetic poles 13 and third rotor-side claw-shaped magnetic poles 33, adifference in generated magnetic fluxes becomes small as compared withthe first embodiment. That is, reverse flow of magnetic fluxes generatedbetween the first rotor-side claw-shaped magnetic poles 13 and the thirdrotor-side claw-shaped magnetic poles 33 whose tip end surfaces 16 and36 abut against each other becomes small as compared with the firstembodiment. According to this, a magnetic flux density of north polesbecomes large as a whole as compared with the first embodiment, northpoles of a magnetic flux density which is larger than that of the firstembodiment is given to the first and third stator-side claw-shapedmagnetic poles 64 and 84 of the opposed stators 2 a.

Similarly, in the second rotor-side claw-shaped magnetic poles 23 andthe fourth rotor-side claw-shaped magnetic poles 43 also, a differencein generated magnetic fluxes becomes small as compared with the firstembodiment. That is, reverse flow of magnetic fluxes generated betweenthe first rotor-side claw-shaped magnetic poles 13 and the thirdrotor-side claw-shaped magnetic poles 33 whose tip end surfaces 26 and46 abut against each other becomes small as compared with the firstembodiment. According to this, a magnetic flux density of south polesbecomes large as a whole as compared with the first embodiment, andsouth poles of a magnetic flux density which is larger than that of thefirst embodiment is given to the second and fourth stator-sideclaw-shaped magnetic poles 74 and 94 of the opposed stators 2 a.

According to this, the rotors of the respective phases can give magneticpoles having large magnetic flux densities to the opposed stators, andoutput can further be increased.

In the stator (single stator 2 a) of each of phases, the first to fourthfour stator cores 60, 70, 80 and 90 are stacked on one another in theaxial direction in this order such that the first, central and fourthannular windings 101, 102A and 104 are respectively interposedtherebetween.

At this time, a magnetic flux density of rotating field of the secondstator-side claw-shaped magnetic poles 74 is determined based on the twoannular windings, i.e., the first annular winding 101 and the centralannular winding 102A. A magnetic flux density of rotating field of thethird stator-side claw-shaped magnetic poles 84 is determined based onthe two annular windings i.e., the central annular winding 102A and thefourth annular winding 104.

On the other hand, a magnetic flux density of rotating field of thefirst stator-side claw-shaped magnetic poles 64 is determined based onthe one first annular winding 101. Similarly, a magnetic flux density ofrotating field of the fourth stator-side claw-shaped magnetic poles 94is determined based on the one fourth annular winding 104.

As a result, in the mutually opposed first and third stator-sideclaw-shaped magnetic poles 64 and 84, a difference in generated magneticfluxes of the rotating field becomes small as compared with the firstembodiment. That is, reverse flow of magnetic fluxes generated betweenthe first stator-side claw-shaped magnetic poles 64 and the thirdstator-side claw-shaped magnetic poles 84 whose tip end surfaces 67 and87 abut against each other becomes small as compared with the firstembodiment.

According to this, a magnetic flux density of rotating field becomeslarge as compared with the first embodiment, and a rotating field whichbecomes large is given to the first and third rotor-side claw-shapedmagnetic poles 13 and 33 of the opposed rotors 1 a.

Similarly, in the mutually opposed second and fourth stator-sideclaw-shaped magnetic poles 74 and 94, a difference in generated magneticfluxes of the rotating field becomes small as compared with the firstembodiment. That is, reverse flow of magnetic fluxes generated betweenthe second stator-side claw-shaped magnetic poles 74 and the fourthstator-side claw-shaped magnetic poles 94 whose tip end surfaces 77 and97 abut against each other becomes small as compared with the firstembodiment.

According to this, a magnetic flux density of rotating field becomeslarge as compared with the first embodiment, and the rotating fieldwhich becomes large is given to the second and fourth rotor-sideclaw-shaped magnetic poles 23 and 43 of the opposed rotors 1 a.

According to this, the stators of the respective phases can give therotating field having large magnetic flux densities to the opposedrotors, and output can further be increased.

FIG. 28 shows characteristic curves for comparison between torquecharacteristics of brushless motors M of the first embodiment and thethird embodiment.

A characteristic curve L1 shows torque characteristics of the brushlessmotor M of the first embodiment, and a characteristic curve L3 showstorque characteristics of the brushless motor M of the third embodiment.Experiment conditions of the two embodiments are the same except thenumber of field magnets and the number of annular windings.

From a result of this experiment, it can be understood that a brushlessmotor M of higher torque is obtained based on the above-describedreasons.

As described above in detail, the third embodiment has the followingadvantages in addition to the advantages of the first embodiment.

(10) According to the third embodiment, the one central field magnet 52Awhich is the same as the first field magnet 51 and the fourth fieldmagnet 54 is placed between the second rotor core 20 and the third rotorcore 30.

Reverse flow of magnetic fluxes between the first rotor-side claw-shapedmagnetic poles 13 and the third rotor-side claw-shaped magnetic poles33, and reverse flow of magnetic fluxes between the second rotor-sideclaw-shaped magnetic poles 23 and the fourth rotor-side claw-shapedmagnetic poles 43 both based on a difference in generated magneticfluxes are suppressed.

Therefore, the rotors of the respective phases can give magnetic poleshaving a large magnetic flux density to the opposed stators, and outputcan further be increased.

(11) According to the third embodiment, the one central annular winding102A which is the same as the first annular winding 101 and the fourthannular winding 104 is placed between the second stator core 70 and thethird stator core 80.

Reverse flow of magnetic fluxes between the first stator-sideclaw-shaped magnetic poles 64 and the third stator-side claw-shapedmagnetic poles 84, and reverse flow of magnetic fluxes between thesecond stator-side claw-shaped magnetic poles 74 and the fourthstator-side claw-shaped magnetic poles 94 both based on a difference ingenerated magnetic fluxes are suppressed.

Therefore, the stators of the respective phases can give the rotatingfield having a large magnetic flux density to the opposed rotors, andoutput can further be increased.

Fourth Embodiment

A fourth embodiment will be described below in accordance with FIGS. 29to 34.

The fourth embodiment is different from the third embodiment, and ischaracterized in that tip end surfaces 16 of first rotor-sideclaw-shaped magnetic poles 13 and tip end surfaces 36 of thirdrotor-side claw-shaped magnetic poles 33 are not made to abut againsteach other but are closely opposed to each other, and tip end surfaces26 of second rotor-side claw-shaped magnetic poles 23 and tip endsurfaces 46 of fourth rotor-side claw-shaped magnetic poles 43 are notmade to abut against each other but are closely opposed to each other.

Further, the fourth embodiment is characterized in that tip end surfaces67 of first stator-side claw-shaped magnetic poles 64 and tip endsurfaces 87 of third stator-side claw-shaped magnetic poles 84 are notmade to abut against each other but are closely opposed to each other,and tip end surfaces 77 of second stator-side claw-shaped magnetic poles74 and tip end surfaces 97 of fourth stator-side claw-shaped magneticpoles 94 are not made to abut against each other but are closely opposedto each other.

Therefore, in the fourth embodiment, the characteristic portions will bedescribed in detail, the same reference numerals as those of the thirdembodiment are allocated to members of common portions, and detaileddescription thereof will be omitted for the sake of convenience ofdescription.

As shown in FIG. 29, each of single motors Ma of respective phasesconfiguring a three-phase brushless motor M includes a single rotor 1 aand a single stator 2 a.

(Single Rotor 1 a)

As shown in FIG. 30A, thicknesses of first, central and fourth fieldmagnets 51, 52A and 54 are the same as those of the third embodiment. Onthe other hand, lengths of first to fourth rotor-side claw-shapedmagnetic poles 13, 23, 33 and 43 are less than 2.5 times of thicknesses(lengths in axial direction) of first to fourth rotor core bases 11, 21,31 and 41.

Therefore, as shown in FIGS. 29 and 30A, the tip end surfaces 16 of thefirst rotor-side claw-shaped magnetic poles 13 and the tip end surfaces36 of the third rotor-side claw-shaped magnetic poles 33 are closelyopposed to each other in an axial direction of the rotor, i.e., opposedto each other in the axial direction such that gaps G of a certaindistance are formed therebetween. Similarly, the tip end surfaces 26 ofthe second rotor-side claw-shaped magnetic poles 23 and the tip endsurfaces 46 of the fourth rotor-side claw-shaped magnetic poles 43 areclosely opposed to each other in an axial direction of the rotor, i.e.,opposed to each other in the axial direction such that gaps G of acertain distance are formed therebetween.

That is, the single rotor 1 a of the fourth embodiment is a of a Lundelltype structure having the gaps G between the tip end surfaces 16 and 36of the first and third rotor-side claw-shaped magnetic poles 13 and 33,and between the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43.

As shown in FIGS. 31 and 32, the single rotors 1 a are used as a U-phaserotor 1 u, a V-phase rotor 1 v and a W-phase rotor 1 w and these rotorsare stacked on one another in the axial direction to form the rotor 1 ofthe three-phase brushless motor M as in the third embodiment.

At this time, as in the third embodiment, the U-phase rotor 1 u and theW-phase rotor 1 w are placed such that placement directions of first tofourth rotor cores 10, 20, 30 and 40 become the same. On the other hand,the V-phase rotor 1 v which is stacked between the U-phase rotor 1 u andthe W-phase rotor 1 w is placed such that placement directions of thefirst to fourth rotor cores 10, 20, 30 and 40 of the V-phase rotor 1 vbecome opposite from the placement directions of the first to fourthrotor cores 10, 20, 30 and 40 of the U-phase rotor 1 u and the W-phaserotor 1 w.

Further, as shown in FIG. 32, the three-phase rotor 1 including theU-phase rotor 1 u, the V-phase rotor 1 v and the W-phase rotor 1 w isconfigured by stacking the U-phase rotor 1 u, the V-phase rotor 1 v andthe W-phase rotor 1 w on one another such that these rotors 1 u, 1 v and1 w are displaced from one another by 5° in mechanical angle (60° inelectrical angle) as in the third embodiment.

(Single Stator 2 a)

As shown in FIG. 30B, coil lengths (lengths in axial direction) offirst, central and fourth annular windings 101, 102A and 104 are thesame as those of the third embodiment.

On the other hand, lengths of first to fourth stator-side claw-shapedmagnetic poles 64, 74, 84 and 94 in the axial direction are less than2.5 times of thicknesses (lengths in axial direction) of first to fourthstator core bases 61, 71, 81 and 91.

Therefore, as shown in FIGS. 29 and 30B, the tip end surfaces 67 of thefirst stator-side claw-shaped magnetic poles 64 and the tip end surfaces87 of the third stator-side claw-shaped magnetic poles 84 are closelyopposed to each other in the axial direction, i.e., opposed to eachother in the axial direction such that gaps G of a certain distance areformed therebetween. Similarly, the tip end surfaces 77 of the secondstator-side claw-shaped magnetic poles 74 and the tip end surfaces 97 ofthe fourth stator-side claw-shaped magnetic poles 94 are closely opposedto each other in the axial direction, i.e., opposed to each other in theaxial direction such that gaps G of a certain distance are formedtherebetween.

That is, the single stator 2 a of the fourth embodiment is of a Lundelltype structure having the gaps G between the tip end surfaces 67 and 87of the first and third stator-side claw-shaped magnetic poles 64 and 84,and between the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94.

As shown in FIGS. 33 and 34, the single stators 2 a are used as aU-phase stator 2 u, a V-phase stator 2 v and a W-phase stator 2 w andthese stators 2 u, 2 v and 2 w are stacked on one another in the axialdirection to form the stator 2 of the three-phase brushless motor M asin the first embodiment.

At this time, as in the third embodiment, of the three-phase stator 2including the U-phase stator 2 u, the V-phase stator 2 v and the W-phasestator 2 w is configured by stacking the U-phase stator 2 u, the V-phasestator 2 v and the W-phase stator 2 w on one another such that they aredisplaced from one another by 5° in mechanical angle (60° in electricalangle).

U-phase AC current Iu of a three-phase AC power source flows through theU-phase stator 2 u. V-phase AC current Iv of the three-phase AC powersource flows through the V-phase stator 2 v. Further, W-phase AC currentIw of the three-phase AC power source flows through the W-phase stator 2w.

Next, operations of the brushless motor M of the fourth embodimenthaving the above-described configuration will be described.

A magnetic flux density of the second rotor-side claw-shaped magneticpoles 23 is determined based on the two field magnets, i.e., the firstfield magnet 51 and the central field magnet 52A. A magnetic fluxdensity of the third rotor-side claw-shaped magnetic poles 33 isdetermined based on the two field magnets, i.e., the central fieldmagnet 52A and the fourth field magnet 54.

On the other hand, a magnetic flux density of the first rotor-sideclaw-shaped magnetic poles 13 is determined based on the one first fieldmagnet 51. Similarly, a magnetic flux density of the fourth rotor-sideclaw-shaped magnetic poles 43 is determined based on the one fourthfield magnet 54.

As a result, in the mutually opposed first rotor-side claw-shapedmagnetic poles 13 and third rotor-side claw-shaped magnetic poles 33, adifference in generated magnetic fluxes becomes small. Further, sincethe tip end surfaces 16 and 36 are closely opposed to each other,reverse flow of magnetic fluxes generated between the first rotor-sideclaw-shaped magnetic poles 13 and the third rotor-side claw-shapedmagnetic poles 33 further becomes small as compared with a case wherethe tip end surfaces 16 and 36 abut against each other.

According to this, since reverse flow of magnetic fluxes is suppressedto a smaller level, a magnetic flux density of north poles can beincreased.

Similarly, in the second rotor-side claw-shaped magnetic poles 23 andthe fourth rotor-side claw-shaped magnetic poles 43 also, a differencein generated magnetic fluxes becomes small. Further, since the tip endsurfaces 26 and 46 are closely opposed to each other, reverse flow ofmagnetic fluxes generated between the second rotor-side claw-shapedmagnetic poles 23 and the fourth rotor-side claw-shaped magnetic poles43 further becomes small as compared with a case where the tip endsurfaces 26 and 46 abut against each other.

According to this, since reverse flow of magnetic fluxes is suppressedto a smaller level, a magnetic flux density of south poles can beincreased.

According to this, the rotors of the respective phases can give magneticpoles having a large magnetic flux density to the opposed stators, andoutput can be increased.

A magnetic flux density of the second stator-side claw-shaped magneticpoles 74 is determined based on the two annular windings, i.e., thefirst annular winding 101 and the central annular winding 102A. Amagnetic flux density of the third stator-side claw-shaped magneticpoles 84 is determined based on the two annular windings, i.e., thecentral annular winding 102A and the fourth annular winding 104.

On the other hand, a magnetic flux density of the first stator-sideclaw-shaped magnetic poles 64 is determined based on the one firstannular winding 101. Similarly, a magnetic flux density of the fourthstator-side claw-shaped magnetic poles 94 is determined based on the onefourth annular winding 104.

As a result, in the mutually opposed first stator-side claw-shapedmagnetic poles 64 and third stator-side claw-shaped magnetic poles 84, adifference in generated magnetic fluxes becomes small. Further, sincethe tip end surfaces 67 and 87 are closely opposed to each other,reverse flow of magnetic fluxes generated between the first stator-sideclaw-shaped magnetic poles 64 and the third stator-side claw-shapedmagnetic poles 84 further becomes small as compared with a case wherethe tip end surfaces 67 and 87 abut against each other.

According to this, since reverse flow of magnetic fluxes is suppressedto a smaller level, rotating field can be increased.

Similarly, in the mutually opposed second stator-side claw-shapedmagnetic poles 74 and the fourth stator-side claw-shaped magnetic poles94, a difference in generated magnetic fluxes becomes small. Further,since the tip end surfaces 77 and 97 are closely opposed to each other,reverse flow of magnetic fluxes generated between the second stator-sideclaw-shaped magnetic poles 74 and the fourth stator-side claw-shapedmagnetic poles 94 further becomes small as compared with a case wherethe tip end surfaces 77 and 97 abut against each other.

According to this, since reverse flow of magnetic fluxes is suppressedto a smaller level, rotating field can be increased.

According to this, the stators of the respective phases can give largerotating field to the opposed rotors, and output can be increased.

A characteristic curve L4 shown in FIG. 28 shows torque characteristicsof the brushless motor M of the fourth embodiment.

As apparent from FIG. 28, it can be understood that the brushless motorM of higher torque than the brushless motor M of the second embodimentshown in FIG. 21 is obtained.

In FIG. 28, although torque characteristics of the brushless motor M ofthe fourth embodiment are slightly smaller than torque characteristicsof the brushless motor M of the third embodiment, it is conceived thatthis is caused by difference in sizes of the gaps G of the tip endsurfaces 16 and 36 (tip end surfaces 26 and 46) and the gaps G of thetip end surfaces 67 and 87 (tip end surfaces 77 and 97).

That is, if the gaps are excessively large, it is conceived thatvariation is generated in a magnetic flux density distribution in theaxial direction between the claw-shaped magnetic poles. From thisreason, it is necessary to set the gaps G while taking a magnetic fluxdensity distribution in the axial direction into consideration in theclaw-shaped magnetic poles.

As described above in detail, the fourth embodiment has the followingadvantages in addition to the advantages of the third embodiment.

(12) According to the fourth embodiment, the tip end surfaces 16 and 36of the first and third rotor-side claw-shaped magnetic poles 13 and 33are closely opposed to each other in the axial direction, reverse flowof magnetic fluxes between the first rotor-side claw-shaped magneticpoles 13 and the third rotor-side claw-shaped magnetic poles 33 based ona difference in generated magnetic fluxes is suppressed, and a magneticflux density of north poles is increased as a whole. Similarly, the tipend surfaces 26 and 46 of the second and fourth rotor-side claw-shapedmagnetic poles 23 and 43 are closely opposed to each other in the axialdirection, reverse flow of magnetic fluxes between the second rotor-sideclaw-shaped magnetic pole 23 and the fourth rotor-side claw-shapedmagnetic pole 43 based on a difference in generated magnetic fluxes issuppressed, and a magnetic flux density of south poles is increased as awhole.

According to this, the rotors of the respective phases can give magneticpoles having a large magnetic flux density to the opposed stators, andoutput can further be increased.

(13) According to the fourth embodiment, the tip end surfaces 67 and 87of the first and third stator-side claw-shaped magnetic poles 64 and 84are closely opposed to each other in the axial direction, reverse flowof magnetic fluxes between the first stator-side claw-shaped magneticpole 64 and the third stator-side claw-shaped magnetic pole 84 based ona difference in generated magnetic fluxes is suppressed, and a magneticflux density of rotating field is increased as a whole. Similarly, thetip end surfaces 77 and 97 of the second and fourth stator-sideclaw-shaped magnetic poles 74 and 94 are closely opposed to each otherin the axial direction, reverse flow of magnetic fluxes between thesecond stator-side claw-shaped magnetic pole 74 and the fourthstator-side claw-shaped magnetic pole 94 based on a difference ingenerated magnetic fluxes is suppressed, and a magnetic flux density ofrotating field is increased as a whole.

According to this, the stators of the respective phases can giverotating field having a large magnetic flux density to the opposedrotors, and output can further be increased.

(14) According to the fourth embodiment, since the tip end surfaces 16and 36 of the first and third rotor-side claw-shaped magnetic poles 13and 33 are closely opposed to each other in the axial direction,variation in a magnetic flux density distribution can be made small inthe axial direction.

Similarly, since the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 are closely opposed toeach other in the axial direction, variation in a magnetic flux densitydistribution can be made small in the axial direction.

According to this, the rotors of the respective phases can give magneticfluxes of a magnetic flux density distribution having small variation inthe axial direction to the opposed stators, and output can further beincreased.

(15) According to the fourth embodiment, since the tip end surfaces 67and 87 of the first and third stator-side claw-shaped magnetic poles 64and 84 are closely opposed to each other in the axial direction,variation in a magnetic flux density distribution can be suppressed to asmall level in the axial direction.

Similarly, since the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94 are closely opposed toeach other in the axial direction, variation in a magnetic flux densitydistribution can be made small in the axial direction.

As a result, the stators of the respective phases can give magneticfluxes (rotating field) of a magnetic flux density distribution havingsmall variation in the axial direction to the opposed rotors, and outputcan further be increased.

The first to fourth embodiments may be changed as follows.

Although the second field magnet 52 and the third field magnet 53 areseparately configured in the first and second embodiments, the secondfield magnet 52 and the third field magnet 53 may be integrally formedas one field magnet.

Although the second annular winding 102 and the third annular winding103 are separately configured in the first and second embodiments, thesecond annular winding 102 and the third annular winding 103 may beintegrally formed as one annular winding.

The thicknesses of the first to fourth rotor cores 10, 20, 30 and 40 arethe same in the first to fourth embodiments. However, the thicknesses ofthe first to fourth rotor cores 10, 20, 30 and 40 may be different fromeach other within such a range that the tip end surfaces 16 and 36 ofthe first and third rotor-side claw-shaped magnetic poles 13 and 33 abutagainst or are closely opposed to each other, and the tip end surfaces26 and 46 of the second and fourth rotor-side claw-shaped magnetic poles23 and 43 abut against or are closely opposed to each other.

The thicknesses (lengths in axial direction) of the first to fourthfield magnets 51 to 54 are the same in the first and second embodiment.However, the thicknesses (lengths in axial direction) of the first tofourth field magnets 51 to 54 may be different from each other withinsuch a range that the tip end surfaces 16 and 36 of the first and thirdrotor-side claw-shaped magnetic poles 13 and 33 abut against or areclosely opposed to each other, and the tip end surfaces 26 and 46 of thesecond and fourth rotor-side claw-shaped magnetic poles 23 and 43 abutagainst or are closely opposed to each other.

In the second and third field magnets 52 and 53 which are placed atcentral positions in the axial direction and which have small fluxleakage toward outside, thicknesses of the second and third fieldmagnets 52 and 53 may be made thinner (magnetic flux densities thereofmay be smaller) than those of the first and fourth field magnets 51 and54 of course.

Thicknesses of the first to fourth rotor cores 10, 20, 30 and 40 are thesame as those of the first to fourth field magnets 51 to 54 in the firstand second embodiments. However, the thicknesses of the first to fourthrotor cores 10, 20, 30 and 40 may be different from those of the firstto fourth field magnets 51 to 54 within such a range that the tip endsurfaces 16 and 36 of the first and third rotor-side claw-shapedmagnetic poles 13 and 33 abut against or are closely opposed to eachother, and the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 abut against or areclosely opposed to each other.

In this case, it is necessary to change axial lengths of the first tofourth rotor-side claw-shaped magnetic poles 13, 23, 33 and 43.

Thicknesses of the first to fourth stator cores 60, 70, 80 and 90 arethe same in the first to fourth embodiments. However, the thicknesses ofthe first to fourth stator cores 60, 70, 80 and 90 may be different fromeach other within such a range that the tip end surfaces 67 and 87 ofthe first and third stator-side claw-shaped magnetic poles 64 and 84abut against or are closely opposed to each other, and the tip endsurfaces 77 and 97 of the second and fourth stator-side claw-shapedmagnetic poles 74 and 94 abut against or are closely opposed to eachother.

The axial lengths of the first to fourth annular windings 101 to 104 arethe same in the first and second embodiments. However, the axial lengthsof the first to fourth annular windings 101 to 104 may be different fromeach other within such a range that the tip end surfaces 67 and 87 ofthe first and third stator-side claw-shaped magnetic poles 64 and 84abut against or are closely opposed to each other, and the tip endsurfaces 77 and 97 of the second and fourth stator-side claw-shapedmagnetic poles 74 and 94 abut against or are closely opposed to eachother.

In the second and third annular windings 102 and 103 which are placed atcentral positions in the axial direction and which have small fluxleakage toward outside, the axial lengths of the second and thirdannular windings 102 and 103 may be shorter (the winding number may besmaller) than those of the first and fourth annular windings 101 and 104of course.

The thicknesses of the first to fourth stator cores 60, 70, 80 and 90are the same as the axial lengths of the first to fourth annularwindings 101 to 104 in the first and second embodiments. However, thethicknesses of the first to fourth stator cores 60, 70, 80 and 90 may bedifferent from the axial lengths of the first to fourth annular windings101 to 104 within such a range that the tip end surfaces 67 and 87 ofthe first and third stator-side claw-shaped magnetic poles 64 and 84abut against or are closely opposed to each other, and the tip endsurfaces 77 and 97 of the second and fourth stator-side claw-shapedmagnetic poles 74 and 94 abut against or are closely opposed to eachother.

In this case, it is necessary to change axial lengths of the first tofourth stator-side claw-shaped magnetic poles 64, 74, 84 and 94.

The axial lengths of the first and third rotor-side claw-shaped magneticpoles 13 and 33 are the same in the first to fourth embodiments, but thelengths may not be the same if the tip end surfaces 16 and 36 of thefirst and third rotor-side claw-shaped magnetic poles 13 and 33 abutagainst or are closely opposed to each other. According to this, it ispossible to adjust a flowing manner of magnetic fluxes which flowthrough the first and third rotor-side claw-shaped magnetic poles 13 and33, and this is effective for reducing vibration.

Similarly, the axial lengths of the second and fourth rotor-sideclaw-shaped magnetic poles 23 and 43 are the same, but the lengths maynot be the same if the tip end surfaces 26 and 46 of the second andfourth rotor-side claw-shaped magnetic poles 23 and 43 abut against orare closely opposed to each other. According to this, it is possible toadjust a flowing manner of magnetic fluxes which flow through the secondand fourth rotor-side claw-shaped magnetic poles 23 and 43, and this iseffective for reducing vibration.

The axial lengths of the first and third stator-side claw-shapedmagnetic poles 64 and 84 are the same in the first to fourthembodiments, but the lengths may not be the same if the tip end surfaces67 and 87 of the first and third stator-side claw-shaped magnetic poles64 and 84 abut against or are closely opposed to each other. Accordingto this, it is possible to adjust a flowing manner of magnetic fluxeswhich flow through the first and third stator-side claw-shaped magneticpoles 64 and 84, and this is effective for reducing vibration.

Similarly, the axial lengths of the second and fourth stator-sideclaw-shaped magnetic poles 74 and 94 are the same, but the lengths maynot be the same if the tip end surfaces 77 and 97 of the second andfourth stator-side claw-shaped magnetic poles 74 and 94 abut against orare closely opposed to each other. According to this, it is possible toadjust a flowing manner of magnetic fluxes which flow through the secondand fourth stator-side claw-shaped magnetic poles 74 and 94, and this iseffective for reducing vibration.

The first to fourth annular windings 101 to 104 are connected to oneanother in series in the single stator 2 a and single phase AC currentflows therethrough in the first and second embodiments, but the first tofourth annular windings 101 to 104 may be connected to one another inparallel and single phase AC current may flow therethrough.

Of course, a switching circuit for selectively switching between seriesconnection and parallel connection of the first to fourth annularwindings 101 to 104 may be provided, and the series connection andparallel connection may be switched in accordance with output of thesingle motor Ma.

Similarly, for the stators 2 u, 2 v and 2 w of the respective phases ofthe three-phase brushless motor M also, the annular windings may beconnected to one another in parallel, or the connection mode mayselectively be switched between series connection and parallelconnection.

In the third and fourth embodiments, the first, central and fourthannular windings 101, 102A and 104 are connected to one another inseries in the single stator 2 a and single phase AC current flowstherethrough like the first embodiment. Alternatively, the first,central and fourth annular windings 101, 102A and 104 may be connectedto one another in parallel, and single phase AC current may flowtherethrough.

Of course, a switching circuit for selectively switching between seriesconnection and parallel connection of the first, central and fourthannular windings 101, 102A and 104 may be provided, and the connectionmode may be switched in accordance with output of the single motor Ma.

Similarly, in the third and fourth embodiments, for the stators 2 u, 2 vand 2 w of the respective phases of the three-phase brushless motor Malso, the annular windings may be connected to one another in parallel,or the connection mode may selectively be switched between seriesconnection and parallel connection.

In the first to fourth embodiments, the tip end surfaces 16 and 36 ofthe first and third rotor-side claw-shaped magnetic poles 13 and 33 areopposed to each other in the axial direction, and are made to abutagainst or closely opposed to each other. Alternatively, the tip endsurfaces 16 and the tip end surfaces 36 may be displaced from each otherin the circumferential direction by a given distance, and the tip endsurfaces 16 and 36 may be made to abut against or closely opposed toeach other, thereby changing center positions of the magnetic poles.According to this, it is possible to adjust a flowing manner of magneticfluxes which flow through the first and third rotor-side claw-shapedmagnetic poles 13 and 33, and this is effective for reducing vibration.

Similarly, the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 are opposed to eachother in the axial direction, and are made to abut against or closelyopposed to each other. Alternatively, the tip end surface 26 and the tipend surface 46 may be displaced from each other in the circumferentialdirection by a given distance, and the tip end surfaces 26 and 46 may bemade to abut against or closely opposed to each other, thereby changingcenter positions of the magnetic poles. According to this, it ispossible to adjust a flowing manner of magnetic fluxes which flowthrough the second and fourth rotor-side claw-shaped magnetic poles 23and 43, and this is effective for reducing vibration.

In the first to fourth embodiments, the tip end surfaces 67 and 87 ofthe first and third stator-side claw-shaped magnetic poles 64 and 84 areopposed to each other in the axial direction to be made to abut againstor closely opposed to each other. Alternatively, the tip end surface 67and the tip end surface 87 may be displaced from each other in thecircumferential direction by a given distance, and the tip end surfaces67 and 87 may be made to abut against or closely opposed to each other,thereby changing center positions of the magnetic poles. According tothis, it is possible to adjust a flowing manner of magnetic fluxes whichflow through the first and third stator-side claw-shaped magnetic poles64 and 84, and this is effective for reducing vibration.

Similarly, the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94 are opposed to eachother in the axial direction to be made to abut against or closelyopposed to each other. Alternatively, the tip end surface 77 and the tipend surface 97 may be displaced from each other in the circumferentialdirection by a given distance, and the tip end surfaces 77 and 97 may bemade to abut against or closely opposed to each other, thereby changingcenter positions of the magnetic poles. According to this, it ispossible to adjust a flowing manner of magnetic fluxes which flowthrough the second and fourth stator-side claw-shaped magnetic poles 74and 94, and this is effective for reducing vibration.

In the first to fourth embodiments, the stator placed on the outer sideof the single rotor 1 a is the single stator 2 a in which the tip endsurfaces 67 and 87 of the first and third stator-side claw-shapedmagnetic poles 64 and 84 are made to abut against or closely opposed toeach other, and the tip end surfaces 77 and 97 of the second and fourthstator-side claw-shaped magnetic poles 74 and 94 are made to abutagainst or closely opposed to each other.

The stator placed on the outer side of the single rotor 1 a may be of aconventional Lundell type. The conventional Lundell type stator includesone annular winding and two stator cores which sandwich the annularwinding, and stator-side claw-shaped magnetic poles of the two statorcores are alternately placed in the circumferential direction. Ofcourse, the stator placed on the outer side of the single rotor 1 a maynot be of the Lundell type, and may be a multi-phase stator such asthree-phase stator.

In the three-phase motor also, the three-phase rotor 1 of each of theembodiments may be placed on the inner side of the conventional Lundelltype three-phase stator or a three-phase stator which is not of Lundelltype.

In the first to fourth embodiments, the rotor placed on the inner sideof the single stator 2 a is the single rotor 1 a in which tip endsurfaces 16 and 36 of the first and third rotor-side claw-shapedmagnetic poles 13 and 33 are made to abut against or closely opposed toeach other, and the tip end surfaces 26 and 46 of the second and fourthrotor-side claw-shaped magnetic poles 23 and 43 are made to abut againstor closely opposed to each other.

The rotor placed on the inner side of the single stator 2 a may be aconventional Lundell type rotor. The Lundell type rotor includes onefield magnet and two rotor cores which sandwich the field magnet, androtor-side claw-shaped magnetic poles of the two rotor cores arealternately placed in the circumferential direction. Of course, therotor paced on the inner side of the single stator 2 a may not be of theLundell type.

In the three-phase motor also, similarly, the three-phase stator 2 ofeach of the embodiments may be placed on the outer side of aconventional Lundell type three-phase rotor or a three-phase rotor whichis not of the Lundell type.

Although the number of the claw-shaped magnetic poles of the first tofourth rotor cores 10, 20, 30 and 40 is twelve in the first to fourthembodiments, the number may appropriately be changed. Similarly,although the number of claw-shaped magnetic poles of the first to fourthstator cores 60, 70, 80 and 90 is twelve, the number may appropriatelybe changed.

The first to fourth field magnets 51 to 54 are made of ferrite magnet inthe first to fourth embodiments, but these field magnets may be made ofother permanent magnet such as neodymium magnet.

In the first to fourth embodiments, the present invention is embodied inthe inner rotor type single motor Ma and the inner rotor typethree-phase brushless motor M, but the invention may be applied to anouter rotor type single motor and an outer rotor type three-phasebrushless motor.

Fifth Embodiment

A fifth embodiment of the motor having a rotor will be described below.

As shown in FIG. 35, a motor case 112 of a motor 111 includes a bottomedcylindrical housing 113, and a front end plate 114 which closes a front(left side in FIG. 35) opening of the cylindrical housing 113. A circuitaccommodating box 115 is mounted on a rear (right side in FIG. 35) endof the cylindrical housing 113, and a power source circuit such as acircuit substrate is accommodated in the circuit accommodating box 115.A stator 116 is fixed to an inner peripheral surface of the cylindricalhousing 113. The stator 116 includes an armature core 117 having aplurality of radially inwardly extending teeth, and a segment conductor(SC) winding 118 wound around the teeth of the armature core 117. Arotor 121 of the motor 111 includes a rotation shaft 122, and is placedon the inner side of the stator 116. The rotation shaft 122 is anon-magnetic metal shaft, and is rotatably supported by bearings 124 and125. The bearings 124 and 125 are supported by a bottom 113 a of thecylindrical housing 113 and the front end plate 114.

As shown in FIGS. 36 and 37, the rotor 121 includes first and secondrotor cores 131 and 132, and an annular magnet 133 as a field magnet.Arrows shown by solid lines in FIG. 36 show magnetized direction(direction from south pole to north pole) of the annular magnet 133.

As shown in FIGS. 36 and 37, the first rotor core 131 includes asubstantially disk-shaped first core base 131 a and a plurality of(twelve in fifth embodiment) first claw-shaped magnetic poles 131 b(first rotor claw-shaped magnetic poles) arranged on an outer peripheryof the first core base 131 a at equal intervals from one another. Thefirst claw-shaped magnetic poles 131 b project radially outward andextend in an axial direction of the rotor.

As shown in FIGS. 36 and 37, the second rotor core 132 has the sameshape as that of the first rotor core 131, and includes a substantiallydisk-shaped second core base 132 a and a plurality of second claw-shapedmagnetic poles 132 b (second rotor claw-shaped magnetic poles) arrangedon an outer periphery of the second core base 132 a at equal intervalsfrom one another. The second claw-shaped magnetic poles 132 b projectradially outward and extend in the axial direction. The second rotorcore 132 is assembled together with the first rotor core 131 such thatthe second claw-shaped magnetic poles 132 b are placed between thecorresponding first claw-shaped magnetic poles 131 b and the annularmagnet 133 is placed (sandwiched) between the first core base 131 a andthe second core base 132 a in the axial direction. The number of firstand second claw-shaped magnetic poles 131 b and 132 b (first and secondrotor claw-shaped magnetic poles) of the rotor 121 and the number of thefirst and second claw-shaped magnetic poles (first and second statorclaw-shaped magnetic poles) of the stator 116 are the same.

As shown in FIGS. 36 and 37, an outer diameter of the annular magnet 133is substantially equal to outer diameters of the first and second corebases 131 a and 132 a. The annular magnet 133 is magnetized in the axialdirection such that the annular magnet 133 causes the first claw-shapedmagnetic poles 131 b to function as first magnetic poles (north poles infifth embodiment), and causes the second claw-shaped magnetic poles 132b function as second magnetic poles (south poles in fifth embodiment).Therefore, the rotor 121 of the fifth embodiment is of so-called Lundelltype structure using the annular magnet 133 as the field magnet. In therotor 121, first claw-shaped magnetic poles 131 b which are north polesand the second claw-shaped magnetic poles 132 b which are south polesare alternately placed in the circumferential direction, and the numberof magnetic poles is twenty four (the number of pairs of poles istwelve).

A through hole 133 a is formed in a center of the annular magnet 133,and the rotation shaft 122 is inserted through the through hole 133 a.An inner diameter r2 of the through hole 133 a is larger than an outerdiameter r1 of the rotation shaft 122. An outer diameter of the annularmagnet 133 is substantially equal to the outer diameters of the firstand second core bases 131 a and 132 a as described above. An annularnon-magnetic (rubber material in fifth embodiment) portion 134 isprovided between the outer peripheral surface 133 b of the annularmagnet 133 and inner surfaces 131 c and 132 c of the claw-shapedmagnetic poles 131 b and 132 b. Hence, since the annular magnet 133abuts against the non-magnetic portion 134 in the radial direction, theannular magnet 133 is sandwiched in the radial direction, and theannular magnet 133 is restrained from moving in the radial direction.

In the motor 111 configured as described above, if three-phase drivecurrent is supplied to the segment conductor (SC) winding 118 throughthe power source circuit in the circuit accommodating box 115, magneticfield for rotating the rotor 121 by the stator 116 is generated, and therotor 121 is rotated and driven.

Next, operations of the motor 111 of the fifth embodiment will bedescribed.

The motor 111 of the fifth embodiment includes the non-magnetic portion134 provided radially between the annular magnet 133 as the field magnetand the claw-shaped magnetic poles 131 b and 132 b of the first andsecond rotor cores 131 and 132 configuring the rotor 121. Thenon-magnetic portion 134 abuts against the claw-shaped magnetic poles131 b and 132 b and the annular magnet 133 in the radial direction. Thenon-magnetic portion 134 comes, under pressure, into contact with (iscompressed between) the annular magnet 133 and the claw-shaped magneticpoles 131 b and 132 b. Hence, the annular magnet 133 can be positionedsuch that it is sandwiched from radially outside without applying anexcessive load to the annular magnet 133. At this time, since thenon-magnetic portion 134 is made of non-magnetic rubber material, themagnetic fluxes are restrained from being short circuited through thenon-magnetic portion 134.

Next, advantages of the fifth embodiment will be described.

(16) The non-magnetic portion 134 which positions the annular magnet 133in the radial direction is provided between the claw-shaped magneticpoles 131 b and 132 b and the annular magnet 133. Hence it is possibleto restrain the magnetic fluxes from being short circuited, to positionand fix the annular magnet 133 in the radial direction, and to restrainthe annular magnet 133 from rattling.

(17) Since the non-magnetic portion 134 is made of rubber material, thenon-magnetic portion 134 can come into contact, under pressure, with theclaw-shaped magnetic poles 131 b and 132 b and the annular magnet 133therebetween, and it is possible to prevent the annular magnet 133 fromdeviating in position in the circumferential direction.

(18) The inner diameter r2 of the through hole 133 a of the annularmagnet 133 is larger than the outer diameter r1 of the rotation shaft122. Hence, it is possible to position and fix the annular magnet 133 bythe non-magnetic portion 134 without press-fitting the rotation shaft122.

(19) Since the non-magnetic portion 134 has the annular shape, it canabut against the disk-shaped annular magnet 133 over its entirecircumference in the radial direction. Hence, it is possible to morereliably restrain the annular magnet 133 from deviating in position.Since the non-magnetic portion 134 has the annular shape, even if theannular magnet 133 as the field magnet cracks, it is possible torestrain the magnet 133 from scattering. Further, since the non-magneticportion 134 is made of rubber material as described above, thenon-magnetic portion 134 can come into contact under pressure, and it ispossible to enhance its hermeticity, and to further restrain the magnet133 from scattering.

The fifth embodiment may be changed as follows.

Although it is not especially mentioned in the fifth embodiment,engagement projections which engage with the claw-shaped magnetic poles131 b and 132 b may be arranged on the non-magnetic portion 134 as shownin FIGS. 39A to 40B. More specifically, as shown in FIG. 39A, engagementprojections 134 a projecting radially outward may be formed on a radialouter surface of the non-magnetic portion 134. According to thisconfiguration, engagement projections 134 b and the claw-shaped magneticpoles 131 b and 132 b engage with each other in the radial direction asshown in FIG. 39B. Engagement projections 134 b projecting in the axialdirection may be formed on an axial end surface of the non-magneticportion 134 as shown in FIG. 40A. According to this configuration, theengagement projections 134 b and the claw-shaped magnetic poles 131 band 132 b engage with each other in the radial direction as shown inFIG. 40B. As described above, if the engagement projections 134 a or 134b are provided and the non-magnetic portion 134 and the claw-shapedmagnetic poles 131 b and 132 b are engaged with each other in the radialdirection, it is possible to more reliably prevent the non-magneticportion 134 from rotating. Hence, it is possible to more reliablyprevent the annular magnet 133 from relatively rotating, and it ispossible to restrain the annular magnet 133 from deviating in positionin the circumferential direction.

Although the axial lengths of the annular magnet 133 and thenon-magnetic portion 134 are substantially equal to each other in thefifth embodiment, the present invention is not limited to thisconfiguration. As shown in FIG. 38 for example, an axial length AL2 ofthe non-magnetic portion 134 may be longer than an axial length AL1 ofthe annular magnet 133. According to this configuration, the annularmagnet can be separated away from the first and second rotor cores, andit is possible to restrain the annular magnet from being damaged.

Although the non-magnetic portion 134 is formed into the annular shapein the fifth embodiment and the other examples, the invention is notlimited to this configuration. That is, a plurality of rod-shapednon-magnetic portions may be provided in the circumferential directionfor example. Alternatively, the non-magnetic portion 134 may integrallybe formed on the first rotor core 131, the second rotor core 132 or theannular magnet 133.

Although the non-magnetic portion 134 is made of rubber material in thefifth embodiment, the material may appropriately be changed only if itis non-magnetic material. For example, the non-magnetic portion 134 maybe made of non-magnetic metal such as stainless steel (SUS), copper andbrass. When the non-magnetic portion 134 is made of non-magnetic metal,the non-magnetic portion 134 including engagement projections 134 c (seeFIGS. 41A and 41B) are punched out from metal sheet material. Thepunched material can be formed into an annular shape to form the annularnon-magnetic portion 134 as shown in FIG. 41A. A shape of the engagementprojection 134 c may be substantially semi-circular shape as viewed fromthe radial direction as shown in FIG. 41B, or may be polygonal shapesuch as triangular shape and rectangular shape.

Although the segment conductor (SC) winding 118 is employed as thewinding in the fifth embodiment, the winding is not limited to this.

Sixth Embodiment

A sixth embodiment of the motor will be described below in accordancewith FIGS. 42 to 44. As show in FIG. 42, the motor is of multi-Lundelltype structure and has a rotor and a stator both of which are of Lundelltype structure. In this motor, a rotation shaft 201 is rotatablysupported by a motor housing (not shown), and rotor portions ofthree-layer structure, i.e., rotor portions 203 u, 203 v and 203 w arestacked in an axial direction of the rotation shaft 201 to configure therotor 204.

The stator 206 of three-layer structure accommodated in a case 212 isplaced around the rotor 204, and the case 212 is fixed to the motorhousing.

The rotor portions 203 u, 203 v and 203 w have the same configurations.Each of the rotor portions 203 u, 203 v and 203 w has such a structurethat substantially disk-shaped rotor cores 207 a and 207 b sandwich bothupper and lower surfaces of a disk-shaped main magnet 208 in the axialdirection. A plurality of (twelve for example) claw-shaped magneticpoles 202 a are arranged on an outer periphery of the rotor core 207 aat equal intervals from one another. The claw-shaped magnetic poles 202a extend toward the rotor core 207 b along the axial direction of therotation shaft 201. A plurality of (twelve for example) claw-shapedmagnetic poles 202 a are arranged on an outer periphery of the rotorcore 207 b at equal intervals from one another. The claw-shaped magneticpoles 202 a extend toward the rotor core 207 a along the axial directionof the rotation shaft 201.

The claw-shaped magnetic poles 202 a and 202 b are magnetized by themain magnet 208 into different polarities, and project from the rotorcores 207 a and 207 b in a staggered manner. According to this, therotor portions 203 u, 203 v and 203 w having twenty four poles areformed for example.

The rotation shaft 201 is relatively non-rotatably inserted throughcenter portions of the rotor portions 203 u, 203 v and 203 w configuredin this manner in a state where the claw-shaped magnetic poles 202 a and202 b of the rotor portions 203 u, 203 v and 203 w are positioned suchthat they are displaced from one another by 60° in electrical angle.

The stator 206 includes stator portions 205 u, 205 v and 205 w. Each ofthe stator portions 205 u, 205 v and 205 w includes annular stator cores210 a and 210 b, and a plurality of (twelve for example) claw-shapedmagnetic poles 209 a and 209 b which are arranged on inner peripheriesof the stator cores 210 a and 210 b, respectively. Like the claw-shapedmagnetic poles 202 a and 202 b of the rotor cores 207 a and 207 b, theclaw-shaped magnetic poles 209 a and 209 b vertically project from thestator cores 210 a and 210 b in a staggered manner.

Annular windings 211 u, 211 v and 211 w extending along thecircumferential direction of the stator cores 210 a and 210 b aremounted between the stator cores 210 a and 210 b. Three layer AC currentcan be supplied to the annular windings 211 u, 211 v and 211 w.

Disk-shaped auxiliary magnets 213 a and 213 b having the same diametersas that of the main magnet 208 are respectively stacked on an uppersurface of the rotor core 207 a of the uppermost rotor portion 203 u anda lower surface of the rotor core 207 b of the lowermost rotor portion203 w.

Thicknesses t1 of the auxiliary magnets 213 a and 213 b are set in arange of 0.1×t0<t1<0.6×t0 when a thickness of the main magnet 208 isdefined as t0.

The auxiliary magnet 213 a is magnetized such that polarity of the lowersurface of the auxiliary magnet 213 a becomes the same as that of theupper surface of the main magnet 208 of the rotor portion 203 u, and theauxiliary magnet 213 b is magnetized such that polarity of the uppersurface of the auxiliary magnet 213 b becomes the same as that of thelower surface of the main magnet 208 of the rotor portion 203 w.

According to this configuration, a magnetic flux distribution betweenthe upper layer rotor portion 203 u and the stator portion 205 u, and amagnetic flux distribution between the intermediate layer rotor portion203 v and stator portion 205 v are equalized. Further, a magnetic fluxdistribution between the lower layer rotor portion 203 w and the statorportion 205 w, and a magnetic flux distribution between the intermediatelayer rotor portion 203 v and stator portion 205 v are equalized.

FIG. 43 shows measured values T obtained by measuring variation inaverage torque when a ratio t1/t0 is varied, wherein t0 is the thicknessof the main magnet 208 and t1 is the thicknesses of the auxiliarymagnets 213 a and 213 b. In the measured values T, average torque whenthe auxiliary magnets 213 a and 213 b are not provided is 100.

As shown in FIG. 43, the average torque exceeds 103% when t1/t0 is in arange A of 0.1 to 0.6, and when t1/t0 is about 0.24, the average torqueexceeds 105% and becomes the maximum value.

Similarly, FIG. 44 shows measured values R obtained by measuringvariation in ripple factor (pt) when the ratio t1/t0 is varied, whereint0 is the thickness of the main magnet 208 and t1 is the thicknesses ofthe auxiliary magnets 213 a and 213 b. In the measured values R, ripplefactor when the auxiliary magnets 213 a and 213 b are not provided is 0,and as the ripple factor is lowered, the measured values R becomesminus.

As shown in FIG. 44, the ripple factor is lowered to about −2 pt in arange A where t1/t0 is 0.1 to 0.6, and when (t1/t0) is about 0.2, theripple factor becomes the minimum value of about −6 pt.

As described above, when t1/t0 is in the range A of 0.1 to 0.6, theaverage torque is reliably enhanced, and the ripple factor is reduced.

According to the motor of the multi-Lundell type structure of the sixthembodiment, the following advantages can be obtained.

(20) Torque ripple of output torque which is output from the rotationshaft 201 can be reduced, and average torque can be enhanced.

(21) Torque ripple of output torque can be reduced, and noise andvibration can be reduced.

(22) As compared with a case where the auxiliary magnets 213 a and 213 bare not provided, average torque can be enhanced by about 3% within therange A where t1/t0 is 0.1 to 0.6.

(23) As compared with a case where the auxiliary magnets 213 a and 213 bare not provided, ripple factor can be lowered to at least about −3 ptwithin the range A where t1/t0 is 0.1 to 0.6.

(24) When t1/t0 is about 0.24, average torque can be enhanced most andcan be 105%.

(25) When t1/t0 is about 0.2, ripple factor can be enhanced most and canbe −6.

The sixth embodiment may be carried out in the following manner.

The rotor portions and the stator portions may not be of three-layerstructure and may be of multi-layer structure.

Seventh Embodiment

A seventh embodiment of the motor will be described below.

FIG. 45 is a perspective view of an entire brushless motor M of theseventh embodiment. An annular stator 313 fixed to a motor housing (notshown) is placed on an outer side of a rotor 312 which is fixed to arotation shaft 311. The brushless motor M is configured by stackingthree single motor portions in an axial direction of the motor, and aU-phase motor portion Mu, a V-phase motor portion My and a W-phase motorportion Mw are stacked from above in this order.

As shown in FIG. 46, the rotor 312 includes three rotors, i.e., aU-phase rotor 312 u, a V-phase rotor 312 v and a W-phase rotor 312 w.The rotors 312 u, 312 v and 312 w have the same configurations.

As shown in FIGS. 46 and 47, each of the rotors 312 u, 312 v and 312 wincludes a first rotor core 314, a second rotor core 315 and a fieldmagnet 316, and is of so-called Lundell type structure. The field magnet316 has a disk shape, and a shaft-through hole 316 a is formed in acenter of the field magnet 316. Both axial end surfaces of the fieldmagnet 316 are flat surfaces.

The first rotor core 314 includes a plurality of (twelve in seventhembodiment) first divided claw-shaped magnetic poles 321 (firstclaw-shaped magnetic poles) which are annularly placed in thecircumferential direction and which have the same shapes. Each of thefirst divided claw-shaped magnetic poles 321 is punched out from adirectional electromagnetic steel plate. Each of the first dividedclaw-shaped magnetic poles 321 includes an extending portion 322 whichextends in the radial direction, and a claw 323 which extends to oneside of the axial direction from radial outer end of the extendingportion 322.

The extending portion 322 of each of the first divided claw-shapedmagnetic poles 321 includes an abutting portion 324 which abuts againstone of axial end surfaces of the field magnet 316, and an outerperipheral projection 325 which projects from the abutting portion 324toward outer peripheries of the motor portions. The abutting portions324 of the first divided claw-shaped magnetic poles 321 are arrangedradially centering on the axis of the rotation shaft 311, and radialinner ends of adjacent abutting portions 324 are fixed to each other byadhesion or welding. A circumferential width of each of the abuttingportions 324 is narrowed toward its inner peripheral side. Innerperipheral end surfaces of the abutting portions 324 configure ashaft-fixing hole 314 a into which the rotation shaft 311 is insertedand fixed. Boundary lines of the adjacent abutting portions 324 formstraight lines extending along the radial direction, and the boundarylines are located at equal intervals from one another in thecircumferential direction.

Each of the outer peripheral projections 325 is located closer to theouter peripheries of the motor portions than an outer peripheral surfaceof the field magnet 316, and the outer peripheral projection 325 doesnot come into contact with the field magnet 316. A circumferential widthof the outer peripheral end of the abutting portion 324 is wider thanthe outer peripheral projection 325. The outer peripheral projection 325is formed into a trapezoidal shape which is narrowed in width toward theouter periphery as viewed from the axial direction.

The claw 323 is formed by bending an outer peripheral end of the outerperipheral projection 325 at right angles, and the outer peripheralsurface of the claw 323 is opposed to the stator 313.

The second rotor core 315 has the same configuration as that of thefirst rotor core 314. That is, the second rotor core 315 includes aplurality of second divided claw-shaped magnetic poles 331 (secondclaw-shaped magnetic poles) including an extending portion 332(including abutting portion 334 and outer peripheral projection 335) anda claw 333. The second divided claw-shaped magnetic poles 331 have thesame shapes as those of the first divided claw-shaped magnetic poles 321of the first rotor core 314.

The first and second rotor cores 314 and 315 are placed such thatprojections of the claws 323 and 333 are opposed to each other, and arecombined with each other such that the claws 323 and 333 are alternatelyarranged at equal intervals from one another in the circumferentialdirection, and such that predetermined gaps are generated between theadjacent claws 323 and 333.

The field magnet 316 is sandwiched between the abutting portions 324 ofthe first divided claw-shaped magnetic poles 321 and the abuttingportions 334 of the second divided claw-shaped magnetic poles 331. Theabutting portions 324 and 334 abut against both axial end surfaces ofthe field magnet 316. One of the axial end surfaces (first axial endsurface) of the field magnet 316 is exposed from gaps between theadjacent abutting portions 324, and the other axial end surface (secondaxial end surface) of the field magnet 316 is exposed from gaps betweenthe adjacent abutting portions 334.

The rotation shaft 311 is inserted through the shaft-through hole 316 aof the field magnet 316, and is inserted through the shaft-fixing holes314 a and 315 a of the rotor cores 314 and 315. The rotation shaft 311is fixed to the field magnet 316 and the rotor cores 314 and 315 byadhesive or the like. An outer peripheral surface of the field magnet316 is opposed to back surfaces (inner peripheral surfaces) of the claws323 and 333 through gaps in the radial direction. The field magnet 316is magnetized in the axial direction such that one axial side surfacethereof which abuts against the first rotor core 314 becomes north poleand one axial side surface thereof which abuts against the second rotorcore 315 becomes south pole. That is, by this field magnet 316, theclaws 323 of the first divided claw-shaped magnetic poles 321 functionas north pole and claws 333 of the second divided claw-shaped magneticpoles 331 function as south poles. A neodymium magnet is used as thefield magnet 316 for example.

The three-phase rotors 312 u, 312 v and 312 w configured as describedabove are of so-called Lundell type structure using the field magnet316. The three-phase rotors 312 u, 312 v and 312 w are stacked on oneanother in the axial direction such that they are displaced from oneanother by 120° in electrical angle (see FIG. 46).

In the seventh embodiment, a stator of so-called Lundell type structureincluding a pair of stator cores 341 and a pair of coil portions 342each including a claw-shaped magnetic pole 341 a is employed for each ofthe stators 313 of the three-phase motor portions Mu, My and Mw (seeFIG. 45). If AC voltage of corresponding phase is applied to the coilportions 342 of the three-phase stators 313, rotating field is generatedand the rotor 312 rotates.

[Producing Method of First and Second Rotor Cores]

A producing method and operations of the first and second rotor cores314 and 315 of the seventh embodiment will be described in accordancewith FIGS. 48 and 49. FIGS. 48 and 49 show a producing manner of thefirst rotor core 314.

As shown in FIG. 48, the plurality of first divided claw-shaped magneticpoles 321 are punched out from an electromagnetic steel plate 350 bymetal punching. At this time, the extending portions 322 and claws 323(not yet bent) are formed on the first divided claw-shaped magneticpoles 321. The plurality of first divided claw-shaped magnetic poles 321are punched out in a state where they are arranged in lines on astraight line such that the extending portions 322 are arranged inparallel to each other. The electromagnetic steel plate 350 is adirectional electromagnetic steel plate which is easily magnetized onlyin one direction. A punching direction is set such that a magneticcharacteristic direction (easily magnetized direction) and alongitudinal direction of the first divided claw-shaped magnetic pole321 (extending portion 322) to be punched match with each other. Themagnetic characteristic direction of the electromagnetic steel plate 350matches with a rolling direction of the electromagnetic steel plate 350.

Next, as shown in FIG. 49, the plurality of punched first dividedclaw-shaped magnetic poles 321 are radially placed such that base endsthereof (ends opposite from the claws) are in contact with each other,and the base ends are fixed to one another through adhesive or welding.

Next, the claws 323 of the plurality of first divided claw-shapedmagnetic poles 321 are bent in the same direction at right angles.According to this, the first rotor core 314 is completed. Since aproducing method of the second rotor core 315 is the same that of thefirst rotor core 314, detailed description thereof will be omitted.

According to this producing method, since the first and second dividedclaw-shaped magnetic poles 321 and 331 are punched out from theelectromagnetic steel plate 350 in a state where they are arranged on astraight line, a waste of the electromagnetic steel plate 350 can bereduced as compared with a case where the rotor core is not divided andthe magnetic poles are punched out in their annular state, and yield isenhanced.

Next, characteristic advantages of the seventh embodiment will bedescribed below.

(26) The first and second divided claw-shaped magnetic poles 321 and 331respectively include the extending portions 322 and 332 extending in theradial direction, and claws 323 and 333 extending in the axial directionfrom radial outer ends of the extending portions 322 and 332. The fieldmagnet 316 is placed between the extending portions 322 and 332 in theaxial direction. The axial one end surface of the field magnet 316 isexposed from the gaps between the extending portions 322, and the axialother end surface of the field magnet 316 is exposed from the gapsbetween the extending portions 332. According to this configuration, itis possible to reduce volumes of the first and second rotor cores 314and 315 as compared with a configuration that disk portions (core bases)which sandwich the field magnet 316 are arranged on the rotor core.According to this, a weight of the rotor can be reduced.

(27) The rotor cores 314 and 315 respectively including the dividedclaw-shaped magnetic poles 321 and 331 which are divided from eachother. According to this, it is possible to configure the rotor cores314 and 315 by punching the plurality of divided claw-shaped magneticpoles 321 and the plurality of divided claw-shaped magnetic poles 331from the electromagnetic steel plate 350 such that the dividedclaw-shaped magnetic poles 321 and 331 are arranged on a straight line,and by annularly (radially) placing the plurality of divided claw-shapedmagnetic poles 321 and the plurality of divided claw-shaped magneticpoles 331. Hence, a waste of the electromagnetic steel plate 350 can bereduced as compared with a case where the rotor core is not divided inthe circumferential direction and the magnetic poles are punched outfrom a steel plate. As a result, yield can be enhanced. By dividing therotor cores 314 and 315 for every divided claw-shaped magnetic pole,magnetic fluxes are easily distributed equally for the dividedclaw-shaped magnetic poles. As a result, it can be expected that outputis enhanced and torque pulsation is reduced.

(28) Each of the divided claw-shaped magnetic poles 321 and 331 ispunched out from the electromagnetic steel plate 350 which is thedirectional electromagnetic steel plate and is formed, the magneticcharacteristic direction of the electromagnetic steel plate 350 matcheswith the longitudinal direction of the divided claw-shaped magneticpoles 321 and 331 (extending portions 322 and 332). According to this,magnetic fluxes easily flow in the radial direction in the extendingportions 322 and 332 of the divided claw-shaped magnetic poles 321 and331. As a result, this configuration can contribute enhancement ofoutput.

(29) The claws 323 and 333 of the divided claw-shaped magnetic poles 321and 331 are formed by bending in the axial direction. Hence, the claws323 and 333 can easily be formed.

The seventh embodiment may be changed as follows.

Although the claws 323 and 333 are formed by bending in the seventhembodiment, the claws 323 and 333 may be formed separately from theextending portions 322 and 332 for example.

A fixing method of the first divided claw-shaped magnetic poles 321(second divided claw-shaped magnetic poles 331) to one another is notlimited to adhesion or welding. For example, inner peripheral ends ofthe divided claw-shaped magnetic poles 321 and 331 (inner peripheralends of abutting portions 324 and 334) are projected axially outward(direction opposite from field magnet). The first divided claw-shapedmagnetic poles 321 (second divided claw-shaped magnetic poles 331) maybe connected to one another by collectively fitting the projectingportions of the inner peripheral ends into an annular connecting member.

In the seventh embodiment, the plurality of divided claw-shaped magneticpoles 321 (331) are punched and formed and then, they are connected toone another, thereby forming the rotor core 314 (315), but the presentinvention is not limited to this configuration. For example, the rotorcore may be punched in a state where the claw-shaped magnetic poles arenot divided and are integral as shown in FIG. 50 for example. That is,the present invention is not limited to the configuration that theclaw-shaped magnetic poles are divided for each of magnetic poles as inthe seventh embodiment.

The number of the divided claw-shaped magnetic poles 321 and 331 (i.e.,number of magnetic poles) is not limited to the seventh embodiment, andthe number may appropriately be changed in accordance withconfigurations.

Although the present invention is embodied in the inner rotor typebrushless motor M in which the rotor 312 is placed on the side of theinner periphery of the stator 313 in the seventh embodiment, theinvention is not especially limited to this configuration. The inventionmay be embodied in an outer rotor type motor in which the rotor isplaced on the side of an outer periphery of the stator.

Eighth Embodiment

An eighth embodiment of the motor will be described below.

As shown in FIG. 51, a motor M of the eighth embodiment includes a rotor410 fixed to a rotation shaft (not shown), and an annular stator 420placed on the outer side of the rotor 410.

[Configuration of Rotor]

As shown in FIGS. 52, 53 and 54, the rotor 410 includes a U-phase rotor410 u, a V-phase rotor 410 v and a W-phase rotor 410 w (three-phasesingle rotors) arranged in the axial direction. The U-phase rotor 410 uincludes a U-phase rotor core 411 u and a field magnet 412 u. TheV-phase rotor 410 v includes a V-phase rotor core 411 v and a fieldmagnet 412 v. The W-phase rotor 410 w includes a W-phase rotor core 411w and a field magnet 412 w.

The U-phase rotor core 411 u includes substantially disk-shaped firstand second core bases 413 u and 414 u which sandwich the field magnet412 u in the axial direction, and a plurality of first claw-shapedmagnetic poles 415 u and a plurality of second claw-shaped magneticpoles 416 u respectively arranged on outer peripheries of the core bases413 u and 414 u. The plurality of first claw-shaped magnetic poles 415 uand the plurality of second claw-shaped magnetic poles 416 u arealternately arranged in the circumferential direction. Similarly, theV-phase rotor core 411 v includes substantially disk-shaped first andsecond core bases 413 v and 414 v which sandwich the field magnet 412 vin the axial direction, and a plurality of first claw-shaped magneticpoles 415 v and a plurality of second claw-shaped magnetic poles 416 vrespectively arranged on outer peripheries of the core bases 413 v and414 v. The plurality of first claw-shaped magnetic poles 415 v and theplurality of second claw-shaped magnetic poles 416 v are alternatelyarranged in the circumferential direction. Similarly, the W-phase rotorcore 411 w includes substantially disk-shaped first and second corebases 413 w and 414 w which sandwich the field magnet 412 w in the axialdirection, and a plurality of first claw-shaped magnetic poles 415 w anda plurality of second claw-shaped magnetic poles 416 w respectivelyarranged on outer peripheries of the core bases 413 w and 414 w. Theplurality of first claw-shaped magnetic poles 415 w and the plurality ofsecond claw-shaped magnetic poles 416 w are alternately arranged in thecircumferential direction.

As shown in FIG. 54, a fixing hole 417 is formed in radial centers ofthe core bases 413 u and 414 u of the U-phase rotor core 411 u and therotation shaft is fixed to the fixing hole 417. A plurality of (twelvein eighth embodiment) projections 418 are formed on outer peripheraledges of the core bases 413 u and 414 u at equal intervals from oneanother. The projections 418 project radially outward. The projections418 of the first core base 413 u and the projections 418 of the secondcore base 414 u are alternately located in the circumferentialdirection.

The field magnet 412 u sandwiched between the first and second corebases 413 u and 414 u is an annular plate-shaped ferrite magnet forexample. The field magnet 412 u is magnetized in the axial directionsuch that a portion thereof closer to the first core base 413 u becomesnorth pole, and a portion thereof closer to the second core base 414 ubecomes south pole.

The core bases 413 v and 414 v and the field magnet 412 v of the V-phaserotor 410 v have the same shapes as those of the core bases 413 u and414 u and the field magnet 412 u of the U-phase rotor 410 u. The U-phaserotor core 411 u and the V-phase rotor core 411 v are stacked on eachother in the axial direction such that their second core bases 414 u and414 v abut against each other.

The core bases 413 w and 414 w and the field magnet 412 w of the W-phaserotor 410 w also have the same shapes as those of the core bases 413 uand 414 u and the field magnet 412 u of the U-phase rotor 410 u. TheV-phase rotor core 411 v and the W-phase rotor core 411 w are stacked oneach other in the axial direction such that their first core bases 413 vand 413 w abut against each other.

Magnetization directions of the field magnets 412 u and 412 w of theU-phase rotor 410 u and the W-phase rotor 410 w are the same (upward inFIG. 54), and magnetization directions of the field magnet 412 v of theV-phase rotor 410 v are opposite from the magnetization directions ofthe U-phase and W-phase field magnets 412 u and 412 w. That is, in therotors 410 u, 410 v and 410 w, portions of the field magnets 412 u, 412v and 412 w closer to the first core bases 413 u, 413 v and 413 w becomenorth poles, and portions of the field magnets 412 u, 412 v and 412 wcloser to the second core bases 414 u, 414 v and 414 w become southpoles.

In the rotor 410 of the eighth embodiment, an integral part includingthe first core bases 413 u, 413 v and 413 w, the second core bases 414u, 414 v and 414 w and the field magnets 412 u, 412 v and 412 w whichare stacked one another in the axial direction is called a center memberX1. A substantially cylindrical outer peripheral member X2 (annularmember) is fixed to an outer periphery of the center member X1. Theouter peripheral member X2 includes claw-shaped magnetic poles 415 u,415 v, 415 w, 416 u, 416 v and 416 w which are integrally formedtogether. The outer peripheral member X2 is formed in such a manner thatan electromagnetic steel plate is subjected to lightening atpredetermined locations thereof (portions between claw-shaped magneticpoles 415 u to 415 w and 416 u to 416 w in circumferential direction)and then, the electromagnetic steel plate is rolled into an annularshape.

The first claw-shaped magnetic poles 415 u, 415 v and 415 w and thesecond claw-shaped magnetic poles 416 u, 416 v and 416 w are alternatelyplaced at equal intervals from one another in the circumferentialdirection. In the eighth embodiment, the number of the first claw-shapedmagnetic poles 415 u, 415 v and 415 w and the number of the secondclaw-shaped magnetic poles 416 u, 416 v and 416 w are twelve (the sameas that of the projections 418). The U-phase first and secondclaw-shaped magnetic poles 415 u and 416 u, the V-phase first and secondclaw-shaped magnetic poles 415 v and 416 v, and the W-phase first andsecond claw-shaped magnetic pole 415 w and 416 w are arranged in theaxial direction in the order of U-phase, V-phase and W-phase. In theeighth embodiment, all of the claw-shaped magnetic poles 415 u to 415 wand 416 u to 416 w have the same shapes, and the shapes are rectangularas viewed from the radial direction.

As shown in FIGS. 53 and 54, the claw-shaped magnetic poles 415 u and416 u, the claw-shaped magnetic poles 415 v and 416 v and theclaw-shaped magnetic poles 415 w and 416 w are placed such that they aredisplaced from one another in phase by 60° (electrical angle) in thecounterclockwise direction. More specifically, the V-phase claw-shapedmagnetic poles 415 v and 416 v are placed such that they are displacedfrom the U-phase claw-shaped magnetic poles 415 u and 416 u in phase by60° in electrical angle (5° in mechanical angle) in the counterclockwisedirection, and the W-phase claw-shaped magnetic pole 415 w and 416 w areplaced such that they are displaced from the V-phase claw-shapedmagnetic poles 415 v and 416 v in phase by 60° in electrical angle inthe counterclockwise direction.

The first claw-shaped magnetic poles 415 u, 415 v and 415 w and thesecond claw-shaped magnetic poles 416 u, 416 v and 416 w are integrallyformed from one electromagnetic steel plate as described above, and theclaw-shaped magnetic poles 415 u to 415 w and 416 u to 416 w areintegrally connected to one another at predetermined locations. Morespecifically, the U-phase claw-shaped magnetic poles 415 u and 416 u areconnected to the first and second claw-shaped magnetic poles 415 v and416 v (V-phase) which are located on a lower part. The W-phaseclaw-shaped magnetic poles 415 w and 416 w are connected to the firstand second claw-shaped magnetic poles 415 v and 416 v (V-phase) whichare located on an upper part. That is, the claw-shaped magnetic poles415 u to 415 w and 416 u to 416 w are integrally connected to both thefirst and second claw-shaped magnetic poles which are adjacent to eachother in the axial direction.

As shown in FIGS. 52 and 54, the center member X1 including the corebases 413 u to 413 w and 414 u to 414 w and the field magnets 412 u, 412v and 412 w is press fitted into the outer peripheral member X2 which isconfigured as described above.

Lengths of the U-phase claw-shaped magnetic poles 415 u and 416 u in theaxial direction are equal to a length from an end surface of the U-phasefirst core base 413 u which is opposed from an end surface thereofcloser to the magnet to an end surface of the second core base 414 u(surface thereof which abuts against V-phase second core base 414 v)opposite from an end surface thereof closer to the magnet. Similarly,lengths of the V-phase first and second claw-shaped magnetic poles 415 vand 416 v in the axial direction are equal to a length from an endsurface of the V-phase second core base 414 v (surface thereof whichabuts against U-phase second core base 414 u) which is opposed from anend surface thereof closer to the magnet to an end surface of the firstcore base 413 v (surface thereof which abuts against W-phase first corebase 413 w) opposite from an end surface thereof closer to the magnet.Similarly, lengths of the W-phase first and second claw-shaped magneticpoles 415 w and 416 w in the axial direction are equal to a length froman end surface of the W-phase first core bases 413 w (surface thereofwhich abuts against V-phase first core base 413 v) which is opposed froman end surface thereof closer to the magnet to an end surface of thesecond core base 414 w opposite from an end surface thereof closer tothe magnet.

Here, in FIGS. 55 and 56, as one phase rotor and one phase stator, theU-phase rotor 410 u and the U-phase stator 420 u are shown as anexample. As shown in FIGS. 55 and 56, in the U-phase rotor 410 u, theprojections 418 of the first core base 413 u abut, in the radialdirection, against an inner peripheral surface of one axial end (upperend in FIG. 52) of each of the first claw-shaped magnetic poles 415 u,and the projections 418 of the second core base 414 u abut, in theradial direction, against an inner peripheral surface of the other axialend (lower end in FIG. 52) of each of the second claw-shaped magneticpoles 416 u. The first claw-shaped magnetic poles 415 u are separatedaway from the second core base 414 u, and the second claw-shapedmagnetic poles 416 u are separated away from the first core base 413 u.

In the V-phase and W-phase rotors 410 v and 410 w also, the projections418 of the first core bases 413 v and 413 w respectively abut againstthe corresponding first claw-shaped magnetic poles 415 v and 415 w, andthe projections 418 of the second core bases 414 v and 414 wrespectively abut against the corresponding second claw-shaped magneticpoles 416 v and 416 w. A circumferential width of each of theprojections 418 is equal to circumferential widths of the claw-shapedmagnetic poles 415 u to 415 w and 416 u to 416 w.

In the rotors 410 u, 410 v and 410 w configured as described above,portions of the field magnets 412 u and 412 v and 412 w which are northpoles are respectively magnetically connected to the first claw-shapedmagnetic poles 415 u, 415 v and 415 w through the first core bases 413u, 413 v and 413 w. Portions of the field magnets 412 u, 412 v and 412 wwhich are south poles are respectively magnetically connected to thesecond claw-shaped magnetic poles 416 u, 416 v and 416 w through thesecond core bases 414 u, 414 v and 414 w.

According to this, as shown in FIG. 57, the first claw-shaped magneticpoles 415 u, 415 v and 415 w function as north poles, and the secondclaw-shaped magnetic poles 416 u, 416 v and 416 w function as southpoles. In FIG. 57, the first core bases 413 u, 413 v and 413 w and thefirst claw-shaped magnetic poles 415 u, 415 v and 415 w which are northpoles are shown by light dotted patterns, and the second core bases 414u, 414 v and 414 w and the second claw-shaped magnetic poles 416 u, 416v and 416 w which are south poles are shown by dense dotted patterns.That is, the rotors 410 u, 410 v and 410 w are of so-called Lundell typestructure having twenty four poles respectively using the field magnets412 u, 412 v and 412 w.

In the claw-shaped magnetic poles 415 u to 415 w and 416 u to 416 w ofthe outer peripheral member X2, widths of connection portions in whichdifferent polarities are connected to each other (i.e., connectionportions through which the first claw-shaped magnetic poles 415 u to 415w and the second claw-shaped magnetic poles 416 u to 416 w are connectedto each other) are narrower than widths of connection portion in whichthe same polarities are connected to each other (i.e., connectionportions through which the first claw-shaped magnetic poles 415 u to 415w are connected to each other and the second claw-shaped magnetic poles416 u to 416 w are connected to each other).

[Configuration of Stator]

As shown in FIGS. 58 and 59, the stator 420 placed on a radial outerside of the rotor 410 includes three stators, i.e., a U-phase stator 420u, a V-phase stator 420 v and a W-phase stator 420 w. The stators 420 u,420 v and 420 w are stacked on one another in the axial direction inthis order such that they are respectively opposed to the correspondingU-phase rotor 410 u, the V-phase rotor 410 v and the W-phase rotor 410 win the radial direction.

As shown in FIGS. 60 and 61, the stators 420 u, 420 v and 420 w have thesame configurations, and respectively include first and second statorcores 421 and 422 and a coil portion 423.

As shown in FIG. 61, the first stator core 421 includes an annularplate-shaped first stator core base 424, and a cylindrical wall 424 c isarranged on an outer periphery of the first stator core base 424. Thecylindrical wall 424 c extends toward the second stator core 422 alongthe axial direction. Further, twelve first stator-side claw-shapedmagnetic poles 425 are arranged on an inner periphery of the firststator core base 424 at equal intervals from one another. The firststator-side claw-shaped magnetic poles 425 extend toward the secondstator core 422 along the axial direction.

Circumferential end surfaces 425 a and 425 b of the first stator-sideclaw-shaped magnetic poles 425 are flat surfaces, cross sections of thefirst stator-side claw-shaped magnetic poles 425 in a directionintersecting with the axial direction at right angles are sector shapes.

An angle of each of the first stator-side claw-shaped magnetic poles 425in the circumferential direction, i.e., an angle formed between thecircumferential end surfaces 425 a and 425 b with respect to a centeraxis of the rotation shaft (not shown) is set smaller than an angle of agap between the adjacent first stator-side claw-shaped magnetic poles425.

The second stator core 422 includes an annular plate-shaped secondstator core base 426 which is made of the same material and has the sameshape as those of the first stator core base 424. An outer periphery ofthe second stator core base 426 abuts against an annular tip endsurfaces of the cylindrical wall 424 c formed on the first stator core421.

Further, twelve second stator-side claw-shaped magnetic poles 427 arearranged on an inner periphery of the second stator core base 426 atequal intervals from one another. The second stator-side claw-shapedmagnetic poles 427 extend toward the first stator core 421.

Circumferential end surfaces 427 a and 427 b of each of the secondstator-side claw-shaped magnetic poles 427 are flat surfaces, and across section of the second stator-side claw-shaped magnetic pole 427 ina direction intersecting with the axial direction at right angles has asector shape.

An angle of each of the second stator-side claw-shaped magnetic poles427 in the circumferential direction, i.e., an angle formed between thecircumferential end surfaces 427 a and 427 b with respect to the centeraxis of the rotation shaft (not shown) is set smaller than an angle of agap between the adjacent second stator-side claw-shaped magnetic poles427.

That is, a shape of the second stator core 422 is the same as that ofthe first stator core 421 when the cylindrical wall 424 c is omitted.

The second stator core 422 is placed on and fixed to the first statorcore 421 such that the second stator-side claw-shaped magnetic poles 427of the second stator core 422 are located between the first stator-sideclaw-shaped magnetic poles 425 of the first stator core 421 as viewedfrom the axial direction.

The second stator core 422 is assembled together with the first statorcore 421 such that the coil portion 423 is placed between the firststator core 421 and the second stator core 422 in the axial direction.

More specifically, as shown in FIGS. 56 and 61, the coil portion 423 issandwiched between a surface of the first stator core base 424 closer tothe second stator core base 426 (opposed surface 424 a) and a surface ofthe second stator core base 426 closer to the first stator core base 424(opposed surface 426 a).

At this time, one of end surfaces 425 a of each of the first stator-sideclaw-shaped magnetic poles 425 in the circumferential direction and theother end surface 427 b of each of the second stator-side claw-shapedmagnetic poles 427 in the circumferential direction are parallel to eachother along the axial direction. Hence, a gap between both the endsurfaces 425 a and 427 b forms a substantially straight line along theaxial direction. The other end surface 425 b of each of the firststator-side claw-shaped magnetic poles 425 in the circumferentialdirection and the one end surface 427 a of each of the secondstator-side claw-shaped magnetic poles 427 in the circumferentialdirection are parallel to each other along the axial direction. Hence, agap between both the end surfaces 425 b and 427 a forms a substantiallystraight line along the axial direction.

As shown in FIG. 56, the coil portion 423 includes an annular winding428, and the annular winding 428 is incorporated in an annular coilbobbin 429. The coil bobbin 429 has a U-shaped cross section whoseradial inner side opens. An outer diameter of the coil bobbin 429 issubstantially equal to an inner diameter of the cylindrical wall 424 cof the first stator core 421, and an outer peripheral surface of thecoil bobbin 429 in the radial direction abuts against an innerperipheral surface of the cylindrical wall 424 c. An inner diameter ofthe coil bobbin 429 is substantially equal to an outer diameter of thefirst stator-side claw-shaped magnetic pole 425 (second stator-sideclaw-shaped magnetic pole 427), and an inner tip end surface of the coilbobbin 429 in radial direction abuts against outer surfaces of the firststator-side claw-shaped magnetic pole 425 and the second stator-sideclaw-shaped magnetic pole 427.

An outer surface of the coil bobbin 429 closer to the first stator core421 in the axial direction abuts against the opposed surface 424 a ofthe first stator core base 424. An outer surface of the coil bobbin 429closer to the second stator core 422 in the axial direction abutsagainst the opposed surface 426 a of the second stator core base 426.

A thickness (axial length) of the coil bobbin 429 is set to apredetermined thickness in accordance with an axial length of the firststator-side claw-shaped magnetic pole 425 (second stator-sideclaw-shaped magnetic pole 427).

That is, the coil bobbin 429 incorporating the annular winding 428therein is placed between the first stator core 421 and the secondstator core 422. At this time, tip end surfaces 425 c of the firststator-side claw-shaped magnetic poles 425 are flush with the opposedsurface 426 b of the second stator core base 426, and tip end surfaces427 c of the second stator-side claw-shaped magnetic poles 427 are flushwith the opposed surface 424 b of the first stator core base 424. Axiallengths of the first stator-side claw-shaped magnetic pole 425 and thesecond stator-side claw-shaped magnetic pole 427 match with axiallengths of the first claw-shaped magnetic poles 415 u, 415 v and 415 wand the second claw-shaped magnetic poles 416 u, 416 v and 416 w of therotors 410 u, 410 v and 410 w.

In FIG. 61, a pulling-out terminal of the annular winding 428 and aterminal mounting portion of the coil bobbin 429 are omitted for thesake of convenience of description. In accordance with this omission, acut out portion for pulling, to outside, the terminal mounting portionformed on the cylindrical wall 424 c of the first stator core 421 isalso omitted in FIG. 61.

The U-phase, V-phase and W-phase stators 420 u, 420 v and 420 wconfigured as described above are of so-called Lundell type (claw poletype) structure having twenty four poles in which the first and secondstator-side claw-shaped magnetic poles 425 and 427 are excited intomagnetic poles which are different from each other on a moment-to-momentbasis by the annular winding 428 between the first and second statorcores 421 and 422. The U-phase, V-phase and W-phase stators 420 u, 420 vand 420 w are stacked on one another in the axial direction to form thestator 420.

As shown in FIGS. 58 and 59, the U-phase stator 420 u, the V-phasestator 420 v and the W-phase stator 420 w are stacked on one anothersuch that they are displaced from one another by 60° in electrical angle(5° in mechanical angle).

More specifically, the V-phase stator 420 v is fixed to the motorhousing (not shown) such that the V-phase stator 420 v is displaced inphase from the U-phase stator 420 u by 60° in electrical angle in theclockwise direction. The W-phase stator 420 w is fixed to the motorhousing such that the W-phase stator 420 w is displaced in phase fromthe V-phase stator 420 v by 60° in electrical angle in the clockwisedirection.

That is, between the first and second stator-side claw-shaped magneticpoles 425 and 427 and the rotor-side claw-shaped magnetic poles 415 u to415 w and 416 u to 416 w of opposed phases, deviation in thecircumferential direction inclines in opposite directions on the opposedsurfaces.

U-phase power source voltage of three-phase AC power source is appliedto the annular winding 428 of the U-phase stator 420 u, V-phase powersource voltage of three-phase AC power source is applied to the annularwinding 428 of the V-phase stator 420 v, and W-phase power sourcevoltage of three-phase AC power source is applied to the annular winding428 of the W-phase stator 420 w.

Next, operations of the motor M of the eighth embodiment will bedescribed.

When the motor M is driven, three-phase AC power source voltage isapplied to the stator 420. That is, U-phase power source voltage isapplied to the annular winding 428 of the U-phase stator 420 u, V-phasepower source voltage is applied to the annular winding 428 of theV-phase stator 420 v, and W-phase power source voltage is applied to theannular winding 428 of the W-phase stator 420 w. According to this,rotating field is generated in the stator 420 and the rotor 410 isrotated and driven.

Here, corresponding to the three-phase AC power source, the stator 420includes three-part structure of the U-phase, V-phase and W-phasestators 420 u, 420 v and 420 w and correspondingly, the rotor 410 alsoincludes three-part structure of the U-phase, V-phase and W-phase rotors410 u, 410 v and 410 w. According to this, in the stators 420 u, 420 vand 420 w and the rotors 410 u, 410 v and 410 w, the stators 420 u, 420v and 420 w which are opposed to one another in the radial direction andthe stators 420 u, 420 v and 420 w which are arranged in the axialdirection can receive magnetic fluxes of the field magnets 412 u, 412 vand 412 w, and output can be increased.

In the eighth embodiment, while the stators 420 u, 420 v and 420 w aredisplaced from one another by 60° in electrical angle in the clockwisedirection, the U-phase, V-phase and W-phase rotors 410 u, 410 v and 410w of the rotors 410 are displaced from one another by 60° in electricalangle in the counterclockwise direction. That is, between the U-phase,V-phase and W-phase stators 420 u, 420 v and 420 w and the opposedU-phase, V-phase and W-phase rotors 410 u, 410 v and 410 w, deviation inthe circumferential direction inclines in opposite directions on theopposed surfaces.

According to this, the rotors 410 u, 410 v and 410 w of the respectivephases can excellently follow the switching of the first and secondstator-side claw-shaped magnetic poles 425 and 427 caused by AC currentflowing through the annular windings 428 of the respective phases. As aresult, the rotor 410 can excellently rotate.

In the eighth embodiment, a magnetization direction of the field magnet412 v of the V-phase rotor 410 v is opposite from those of the fieldmagnets 412 u and 412 w of the U-phase and W-phase rotors 410 u and 410w. According to this, polarities of both sides of the V-phase fieldmagnet 412 v in the axial direction become the same as those of theU-phase and W-phase field magnets 412 u and 412 w which are opposed toeach other in the axial direction. Hence, magnetic fluxes of the V-phasefield magnet 412 v are less prone to leak toward the U-phase and W-phaserotors 410 u and 410 w. As a result, magnetic fluxes of the V-phasefield magnet 412 v excellently flow toward the first and secondclaw-shaped magnetic poles 415 v and 416 v of the V-phase rotor 410 v.

Further, in the eighth embodiment, since the U-phase, V-phase andW-phase rotors 410 u, 410 v and 410 w of the rotor 410 are of Lundelltype structure, although the field magnets 412 u, 412 v and 412 w havethe same structures, the number of the claw-shaped magnetic poles 415 uto 415 w and 416 u to 416 w (and number of projections 418) can bechanged. Hence, when it is required to change the number of magneticpoles, it is easy to change the number of poles. Similarly, since theU-phase, V-phase and W-phase stators 420 u, 420 v and 420 w of thestator 420 are of claw pole type structure, although the coil portions423 have the same structures, the number of first and second stator-sideclaw-shaped magnetic poles 425 and 427 can be changed. Hence, it is easyto change the number of poles.

That is, according to the brushless motor of the eighth embodiment, itis easy to change the specification of various combinations of thenumber of magnetic poles of the rotor 410 and the stator 420 withoutlargely changing the design.

In the rotor cores 411 u, 411 v and 411 w of the eighth embodiment, thefirst core bases 413 u, 413 v and 413 w and the first claw-shapedmagnetic poles 415 u, 415 v and 415 w are separately configured, and thesecond core bases 414 u, 414 v and 414 w and the second claw-shapedmagnetic poles 416 u, 416 v and 416 w are separately configured.According to this, it is possible to individually form the core bases413 u to 413 w and 414 u to 414 w and the claw-shaped magnetic poles 415u to 415 w and 416 u to 416 w. Hence, it is possible to reduce a wasteof material between the claw-shaped magnetic poles generated when thecore base and the claw-shaped magnetic pole are integrally formed, andyield is enhanced. Further, all of the claw-shaped magnetic poles 415 uto 415 w and 416 u to 416 w are integrally formed into the annular shapefrom one electromagnetic steel plate. Hence, increase in the number ofparts is suppressed and as a result, management of parts does not becomecomplicated.

Next, characteristic advantages of the eighth embodiment will bedescribed below.

(30) In the rotor cores 411 u, 411 v and 411 w, the first claw-shapedmagnetic poles 415 u, 415 v and 415 w and the second claw-shapedmagnetic poles 416 u, 416 v and 416 w are separately configured from thefirst core bases 413 u, 413 v and 413 w and the second core bases 414 u,414 v and 414 w which sandwich the field magnets 412 u, 412 v and 412 win the axial direction. According to this configuration, the core bases413 u to 413 w and 414 u to 414 w and the claw-shaped magnetic poles 415u to 415 w and 416 u to 416 w (outer peripheral member X2) can beseparately formed. Therefore, it is possible to reduce a waste ofmaterial between the claw-shaped magnetic poles generated when the corebase and the claw-shaped magnetic pole are integrally formed, and yieldis enhanced. Further, eddy current which can be generated at a boundarybetween the claw-shaped magnetic poles 415 u to 415 w and 416 u to 416 wand the projection 418 is suppressed, and output of the motor M can beincreased. Further, since the claw-shaped magnetic poles 415 u to 415 wand 416 u to 416 w which are adjacent to each other in the axialdirection are integrally connected to one another between the phases,increase in the number of parts can be suppressed. As a result, this isadvantageous in terms of management of parts.

(31) Since the claw-shaped magnetic poles 415 u to 415 w and 416 u to416 w of the rotors 410 u, 410 v and 410 w configure the integral outerperipheral member X2 (annular member), the number of parts can bereduced. As a result, management of parts becomes easier.

(32) The center member X1 including the core bases 413 u to 413 w and414 u to 414 w and the field magnet 412 u, 412 v and 412 w is pressfitted into the outer peripheral member X2. Hence, the outer peripheralmember X2 and the center member X1 can easily be fixed to each other.

(33) The annular member is formed from one steel plate material(electromagnetic steel plate). Hence, if the steel plate material issubjected to lightening at predetermined locations thereof and it isrolled into the annular shape, the outer peripheral member X2 having theclaw-shaped magnetic poles 415 u to 415 w and 416 u to 416 w can beformed. Therefore, it is possible to easily form the outer peripheralmember X2.

The eighth embodiment may be changed as follows.

In the eighth embodiment, the inner peripheral surfaces of theclaw-shaped magnetic poles 415 u to 415 w and 416 u to 416 w are fixedto the projections 418 formed on the core bases 413 u to 413 w and 414 uto 414 w, but the invention is not limited to this configuration. Asshown in FIG. 62 for example, the projections 418 may be omitted fromthe core bases 413 u to 413 w and 414 u to 414 w of the eighthembodiment, projections 431 projecting radially inward may be formed onthe claw-shaped magnetic poles 415 u to 415 w and 416 u to 416 w, andthe projections 431 may be fixed to the outer peripheral surfaces of thecore bases 413 u to 413 w and 414 u to 414 w. Portions extending in theradial direction like the projections 418 and 431 may be omitted.

Although the claw-shaped magnetic poles 415 u to 415 w and 416 u to 416w are formed into the rectangular shapes as viewed from the radialdirection in the eighth embodiment, the invention is not limited to thisconfiguration. As shown in FIG. 63 for example, the claw-shaped magneticpoles 415 u to 415 w and 416 u to 416 w may be formed into such shapesthat circumferential widths thereof become narrower toward their axialtip ends (axial ends opposite from portions thereof fixed to theprojections 418).

In the eighth embodiment, the claw-shaped magnetic poles 415 u to 415 wand 416 u to 416 w are integrally connected to both the first and secondclaw-shaped magnetic poles of phases which are adjacent to each other inthe axial direction and according to this, the outer peripheral memberX2 which is integrally formed into the annular shape is configured, butthe invention is not limited to this configuration. As shown in FIG. 64for example, the first claw-shaped magnetic poles 415 u, 415 v and 415 wwhich are adjacent to one another in the axial direction are connectedto one another, and the first claw-shaped magnetic poles 415 u, 415 vand 415 w and the second claw-shaped magnetic poles 416 u, 416 v and 416w are separated away from each other. That is, each one of the U-phase,V-phase and W-phase first claw-shaped magnetic poles 415 u, 415 v and415 w configures one integral part. Similarly, the second claw-shapedmagnetic poles 416 u, 416 v and 416 w which are adjacent to one anotherin the axial direction are connected to one another, and each one of theU-phase, V-phase and W-phase second claw-shaped magnetic poles 416 u,416 v and 416 w configures one integral part. As described above, theouter peripheral member X2 shown in FIG. 64 has such a configurationthat integral parts including the first claw-shaped magnetic poles 415u, 415 v and 415 w which are arranged in the axial direction andintegral parts including the second claw-shaped magnetic poles 416 u,416 v and 416 w which are arranged in the axial direction arealternately placed in the circumferential direction, and the firstclaw-shaped magnetic poles 415 u, 415 v and 415 w and the secondclaw-shaped magnetic poles 416 u, 416 v and 416 w having polaritieswhich are different from each other are separated from each other. Inthe example shown in FIG. 64, each of the claw-shaped magnetic poles 415u to 415 w and 416 u to 416 w is tapered toward its axial tip end.

According to this configuration, although the number of parts isincreased as compared with the eighth embodiment, since the firstclaw-shaped magnetic poles 415 u, 415 v and 415 w and the secondclaw-shaped magnetic poles 416 u, 416 v and 416 w having polaritieswhich are different from each other are separated from each other, it ispossible to reduce short circuit magnetic fluxes which do not contributeto rotation of the rotor 410.

In the eighth embodiment, the center member X1 is press fitted into theouter peripheral member X2, and the projections 418 of the core bases413 u to 413 w and 414 u to 414 w are brought into contact with theinner peripheral surfaces of the claw-shaped magnetic poles 415 u to 415w and 416 u to 416 w under pressure, but the invention is not limited tothis configuration. For example, the projections 418 and the innerperipheral surfaces of the claw-shaped magnetic poles 415 u to 415 w and416 u to 416 w may be adhered and fixed to each other.

In the eighth embodiment, the core bases 413 u to 413 w and 414 u to 414w may be formed by stacking core sheets made of steel plate in the axialdirection. The claw-shaped magnetic poles 415 u to 415 w and 416 u to416 w may be formed by stacking core sheets made of steel plate in thecircumferential direction. According to this configuration, it ispossible to reduce a loss in eddy current generated by variation inmagnetic fluxes.

In the eighth embodiment, the present invention is applied to the motorM in which the single rotors (rotors 410 u, 410 v and 410 w) and thesingle stators (stators 420 u, 420 v and 420 w) are of three layerstructure, but the invention may be applied to a motor in which therotors and the stators are of four or more layer structure.

Although the invention is applied to the inner rotor type motor M inwhich the rotor 410 is placed on the inner periphery of the stator 420in the eighth embodiment, the invention may be applied to an outer rotortype motor.

Ninth Embodiment

A ninth embodiment of the motor will be described below.

FIG. 65 is a perspective view of an entire brushless motor M of theninth embodiment. An annular stator 513 fixed to a motor housing (notshown) is placed on the outer side of a rotor 512 fixed to a rotationshaft 511. The brushless motor M is formed by stacking three singlemotor portions, i.e., a U-phase motor portion Mu, a V-phase motorportion Mv and a W-phase motor portion Mw in an axial direction of themotor from above in this order. Each of the motor portions Mu, Mv and Mwincludes a single stator 513 a and a single rotor 512 a (only U-phaserotor is shown in FIG. 65). The stator 513 includes the plurality ofsingle stators 513 a, and the rotor 512 includes the plurality of singlerotors 512 a.

As shown in FIG. 66, the single stator 513 a includes an annular statorcore 514 and a coil portions 515 placed inside of the stator core 514.

The stator core 514 is formed in such a manner that an electromagneticsteel plate is subjected to lightening by metal punching and then,predetermined locations thereof are bent. The stator core 514 includes aplurality of (twelve in ninth embodiment) first claw-shaped magneticpoles 521 arranged at equal intervals from one another in acircumferential direction of the motor, a plurality of (same number asthat of the first claw-shaped magnetic poles 521) second claw-shapedmagnetic poles 522 respectively placed between the first claw-shapedmagnetic poles 521 in the circumferential direction, and a plurality ofcore back portions 523 which connects, to each other, the first andsecond claw-shaped magnetic poles 521 and 522 which are adjacent to eachother in the circumferential direction.

The first claw-shaped magnetic poles 521 include first extendingportions 521 a forming flat portions which are perpendicular to an axisof the rotation shaft 511. Each of the first extending portions 521 ahas a V-shape which opens toward an outer peripheral side of the motoras viewed from the axial direction, and a second extending portion 521 bis located on an inner peripheral end of the first extending portion 521a. The second extending portion 521 b is bent and formed to extendtoward one side of the axial direction.

Each of the second claw-shaped magnetic poles 522 has the same shape asthat of the first claw-shaped magnetic pole 521, and has a firstextending portion 522 a forming a flat portion which is perpendicular tothe axis of the rotation shaft 511, and a second extending portion 522 bwhich extends in the axial direction from an inner peripheral end of thefirst extending portion 522 a.

The second extending portions 521 b and 522 b of the first and secondclaw-shaped magnetic poles 521 and 522 extend toward each other, and arealternately placed at equal intervals from one another in thecircumferential direction. The second extending portions 521 b and 522 bconfigure an inner periphery of the stator core 514, and innerperipheral surfaces of the second extending portions 521 b and 522 b areopposed to the rotor 512 in the radial direction. The second extendingportions 521 b and 522 b are formed into trapezoidal shapes whose widthsbecome narrower toward their tip ends as viewed from the radialdirection so that they do not interfere with each other. Innerperipheral surfaces of the second extending portions 521 b and 522 b areformed into arc shapes centering on the axis of the rotation shaft 511.

In the first extending portion 521 a of the first claw-shaped magneticpoles 521 and the first extending portion 522 a of the secondclaw-shaped magnetic poles 522 which are adjacent to each other in thecircumferential direction, an outer peripheral end of the firstextending portion 521 a and an outer peripheral end of the firstextending portion 522 a are superposed on each other as viewed from theaxial direction, and the superposed portions are connected to each otherthrough the core back portion 523. Each of the core back portions 523 isconnected to corresponding one of opening ends (pair of radial outerends) of the V-shape of the first extending portions 521 a and 522 a.The core back portions 523 configure an outer periphery of the statorcore 514. The first extending portion 521 a of the first claw-shapedmagnetic poles 521 extends toward an inner periphery of the motor fromone of axial ends (upper end in FIG. 66) of the core back portions 523,and the first extending portion 522 a of the second claw-shaped magneticpoles 522 extends toward the inner periphery of the motor from the otheraxial end (lower end in FIG. 66) of the core back portions 523. Thefirst extending portions 521 a and 522 a of the claw-shaped magneticpoles 521 and 522 are bent with respect to the core back portions 523. Acut out portion 525 is formed in each of angle portions 524 formedbetween the core back portions 523 and the first extending portions 521a and 522 a.

Annular coil portions 515 centering on the axis of the rotation shaft511 are placed between the first claw-shaped magnetic poles 521 and thesecond claw-shaped magnetic poles 522 in the axial direction. The coilportions 515 are located between the first extending portions 521 a ofthe first claw-shaped magnetic poles 521 and the first extendingportions 522 a of the second claw-shaped magnetic poles 522, and arelocated between the core back portions 523 and the second extendingportions 521 b and 522 b in the radial direction. The coil portions 515and the stator core 514 are electrically insulated from each other bycoil bobbins (not shown) interposed therebetween. A pulling-out terminal(not shown) of the coil portion 515 is led out from the cut out portion525.

Each of the motor portions Mu, Mv and Mw includes the stator 513 ahaving the above-described configuration. The stator 513 a of each ofthe phases is of so-called Lundell type (claw pole type) structurehaving twenty four poles in which the first and second claw-shapedmagnetic poles 521 and 522 are excited into magnetic poles which aredifferent from each other on a moment-to-moment basis by supplying powerto the coil portion 515. The three-phase stators 513 a are stacked onone another in the axial direction such that they are displaced from oneanother in phase by 60° in electrical angle. If AC voltage ofcorresponding phase is applied to the coil portion 515 of thethree-phase stator 513 a, rotating field is generated and the rotor 512rotates.

In the ninth embodiment, as each of the rotors 512 a of the motorportions Mu, Mv and Mw, a rotor of so-called Lundell type structure inwhich a pair of rotor core 526 having claw-shaped magnetic poles 526 aand a field magnet 527 is employed (see FIG. 65).

[Producing Method of Stator Core]

Next, a producing method and operations of the stator core 514 of theninth embodiment will be described.

As shown in FIG. 67, a plurality of punched materials 531 are firstpunched out from an electromagnetic steel plate 530 (punching step). Atthis time, the first and second claw-shaped magnetic poles 521 and 522and the core back portions 523 are integrally formed with each of thepunched materials 531. The plurality of first claw-shaped magnetic poles521 are formed such that their tip ends (second extending portions 521a) are oriented in the same direction, and the plurality of secondclaw-shaped magnetic poles 522 are formed such that their tip ends(second extending portions 522 a) are oriented in the same direction(direction opposite from the orienting direction of first claw-shapedmagnetic poles 521). When the plurality of punched materials 531 arepunched out from the electromagnetic steel plate 530 as in the ninthembodiment, it is desirable, in terms of enhancement of yield, to set apunching die such that the second claw-shaped magnetic poles 522 areplaced between the first claw-shaped magnetic poles 521 of the adjacentpunched material 531.

The cut out portions 525 extending to central portions of the firstextending portions 521 a and 522 a are formed in boundary portions B1(the portions which become angle portions 524 after bending) between thecore back portions 523 and the first extending portions 521 a and 522 aof the claw-shaped magnetic poles 521 and 522. The cut out portions 525are formed such that the cut out portions sever the first claw-shapedmagnetic poles 521 (first extending portions 521 a) which are adjacentto each other in the circumferential direction and the secondclaw-shaped magnetic poles 522 (first extending portions 522 a) whichare adjacent to each other in the circumferential direction.

Next, an annular-forming step for forming the punched material 531 intoan annular shape is carried out. In this step, the punched material 531is formed into an annular shape, longitudinal (lateral in FIG. 67) firstend 531 a and second end 531 b of the punched material 531 are fixed toeach other through welding (see FIG. 66 also). During thisannular-forming step, the coil portion 515 is placed on the side of theinner periphery of the core back portions 523.

Next, a bending step of bending the first and second claw-shapedmagnetic poles 521 and 522 is carried out. In this step, each of theboundary portions B1 between the core back portions 523 and the firstextending portions 521 a and 522 a of the claw-shaped magnetic poles 521and 522 is bent in the same direction at right angles, thereby formingthe first extending portions 521 a and 522 a. At this time, since thecut out portions 525 are formed in the boundary portion B1, the firstextending portions 521 a and 522 a can easily be bent even if thepunched material 531 is formed into the annular shape. In theclaw-shaped magnetic poles 521 and 522, boundary portions B2 between thefirst extending portions 521 a and 522 a and the second extendingportions 521 b and 522 b are bent in mutually opposed directions atright angles, thereby forming the second extending portions 521 b and522 b. In this manner, the claw-shaped magnetic poles 521 and 522 havingthe first extending portions 521 a and 522 a and the second extendingportions 521 b and 522 b are bent and formed. According to this, thestators 513 a of the ninth embodiment are completed. Then, (three)stators 513 a of the three phases are stacked one another in the axialdirection such that the stators 513 a are displaced from one another inphase by 60° in electrical angle. At this time, it is preferable thatthe stators 513 a of three phases are stacked on one another such thatconnected portions (connected portions between first and second ends 531a and 531 b) of the punched materials 531 in the three-phase stators 513a are located at equal intervals from one another (120°) in thecircumferential direction. According to this, magnetic unbalance whichmay be caused by the connected portion between the punched materials 531is suppressed, and this can contribute to enhancement of motor quality.

According to this producing method, the punched material 531 which ispunched out from the electromagnetic steel plate 530 is formed into theannular shape to form the stator core 514. Therefore, as compared with acase where the stator core is punched out into the annular shape, awaste of the electromagnetic steel plate 530 is reduced, and yield isenhanced.

Next, characteristic advantages of the ninth embodiment will bedescribed below.

(34) The first and second claw-shaped magnetic poles 521 and 522 areintegrally formed as the punched material 531, the punched material 531is formed into the annular shape, both the ends of the punched material531 (first and second ends 531 a and 531 b) are connected to each other,thereby forming the stator core 514. According to this, there is no needto form the punching die of the punched material 531 which configuresthe stator core 514 into the annular shape. Therefore, it is possible toreduce a waste of the electromagnetic steel plate 530 and as a result,yield can be enhanced.

(35) The stator core 514 has the core back portions 523 which configurethe outer periphery of the stator core 514, and the first and secondclaw-shaped magnetic poles 521 and 522 are formed by bending the firstextending portions 521 a and 522 a which extend toward the innerperiphery from the core back portions 523 and by bending the secondextending portions 521 b and 522 b which extend in the axial directionfrom the inner peripheral ends of the first extending portions 521 a and522 a. According to this configuration, the first and second claw-shapedmagnetic poles 521 and 522 can excellently be integrally formed on thestator core 514. Further, opposed areas of the stator 513 a and therotor 512 a can be obtained by the second extending portions 521 b and522 b of the claw-shaped magnetic poles 521 and 522.

(36) The cut out portions 525 are formed in the angle portions 524formed by the core back portions 523 and the first extending portions521 a and 522 a. Hence, the first extending portions 521 a and 522 a caneasily be bent and formed with respect to the core back portions 523which configure the outer periphery of the stator core 514.

The ninth embodiment may be changed as follows.

Configurations (shape and number of claw-shaped magnetic poles 521 and522) of the stator core 514 (punched material 531) are not limited tothe ninth embodiment, and they may appropriately be changed inaccordance with a configuration.

For example, the cut out portions 525 are formed in the boundaryportions B1 (portions which become angle portions 524 after bending)between the core back portions 523 and the first extending portions 521a and 522 a of the claw-shaped magnetic poles 521 and 522 in the ninthembodiment, but the present invention is not limited to thisconfiguration. As shown in FIGS. 68 and 69 for example, holes 541 may beformed instead of the cut out portions 525 of the ninth embodiment.According to this configuration, the first claw-shaped magnetic poles521 (first extending portions 521 a) which are adjacent to each other inthe circumferential direction and the second claw-shaped magnetic poles522 (first extending portions 522 a) which are adjacent to each other inthe circumferential direction are not severed from each other unlike theninth embodiment, and they are connected to each other throughconnecting portions 542. Each of the holes 541 extends from a centralportion of the first extending portion 521 a (first extending portion522 a of second claw-shaped magnetic poles 522) of the first claw-shapedmagnetic poles 521 to the boundary portion B1 between the secondclaw-shaped magnetic poles 522 (first claw-shaped magnetic poles 521)and the core back portion 523. That is, since an end of the hole 541 issuperposed on the boundary portion B1, the first extending portions 521a and 522 a can easily be bent and formed. According to thisconfiguration also, like the ninth embodiment, it is possible to reducea waste of the electromagnetic steel plate 530 and as a result, yieldcan be enhanced.

As shown in FIGS. 70 and 71, slits 544 (cut out portions) extending inthe axial direction may be formed in the angle portions 543 formed bythe first extending portions 521 a and 522 a and the second extendingportions 521 b and 522 b of the first and second claw-shaped magneticpoles 521 and 522. According to this configuration, it becomes easy toform the inner peripheral surfaces (surfaces opposed to rotor 512 a) ofthe second extending portions 521 b and 522 b into arc shapes. If theinner peripheral surfaces of the second extending portions 521 b and 522b are formed into the arc shapes, an air gap between the outerperipheral surface of the rotor 512 a and the inner peripheral surfaceof the stator 513 a can be equalized and as a result, this configurationcan contribute to enhancement of the motor quality. Although the slits544 extend to the tip ends of the second extending portions 521 b and522 b in the example shown in FIGS. 70 and 71, the invention is notlimited to this configuration. Instead of the slits 544, at least holesmay be formed in the angle portions 543.

The connecting configuration of both the ends of the punched material531 (configuration of first and second ends 531 a and 531 b) is notlimited to the ninth embodiment, and the connecting configuration mayappropriately be changed in accordance with a configuration.

In the producing step of the stator core 514, the order of theannular-forming step, the bending step and the placing step of the coilportion 515 is not limited to the ninth embodiment, and the order ofthese steps may be changed.

Although the invention is embodied in the inner rotor type motor M inwhich the rotor 512 is placed on the side of the inner periphery of thestator 513 in the ninth embodiment, the invention may be embodied in anouter rotor type motor in which the rotor is placed on the side of anouter periphery of the stator.

Tenth Embodiment

A tenth embodiment of the motor will be described below.

As shown in FIG. 72, a brushless motor M of the tenth embodiment hassuch a configuration that an annular stator 613 accommodated in a yokehousing H (housing) is placed on the outer side of a rotor 612 fixed toa rotation shaft 611.

As shown in FIGS. 72 and 73, the brushless motor M is formed by stackingthree single motor portions, i.e., a U-phase motor portion Mu, a V-phasemotor portion My and a W-phase motor portion Mw in an axial direction ofthe motor from above in this order. That is, the brushless motor Mincludes a U-phase stator 613 a, a V-phase stator 613 b, a W-phasestator 613 c, and three rotors (only U-phase rotor 612 a is shown inFIG. 72) which are opposed to the respective stators 613 a, 613 b and613 c in a radial direction of the motor.

As shown in FIG. 74, the U-phase stator 613 a in the stator 613 includesa stator core SC including a first core member 614 and a second coremember 615, and a coil portion 616.

More specifically, the first core member 614 includes a substantiallyannular plate-shaped first core base portion 618 arranged on one side(upper side in FIG. 74) in the axial direction, and a substantiallycylindrically-formed cylindrical wall 619 (outer peripheripheralportion) extending from a radial outer end of the first core baseportion 618 toward the other side (lower side in FIG. 74) in the axialdirection. A plurality of (twelve in tenth embodiment) first claw-shapedmagnetic poles 621 are formed on an inner peripheral end (innerperipheral portion) of the first core base portion 618 at equalintervals from one another (30° intervals) in the circumferentialdirection. The first claw-shaped magnetic poles 621 project radiallyinward from the first core base portion 618 and extend in the axialdirection.

As shown in FIGS. 75 and 76, a first positioning convex portion 619 aprojecting radially outward is formed on the cylindrical wall 619. Thefirst positioning convex portion 619 a is formed by cutting out aportion of the cylindrical wall 619 and by bending the cut out portionradially outward substantially at right angles. According to this, a cutout portion 619 b is formed at a position of the cylindrical wall 619which corresponds to the first positioning convex portion 619 a, andinside and outside of the cylindrical wall 619 in the radial directionare brought into communication with each other through the cut outportion 619 b. The first positioning convex portion 619 a and the cutout portion 619 b are formed into rectangular shapes.

The first positioning convex portion 619 a is formed at a positioncorresponding to a circumferential center of one of the plurality offirst claw-shaped magnetic poles 621 (first claw-shaped magnetic pole621 a in FIG. 75). More specifically, the first positioning convexportion 619 a is formed on a circumferential center line L1 of the firstclaw-shaped magnetic pole 621 a as viewed from the axial direction.

As shown in FIGS. 73 to 75, the second core member 615 has substantiallythe same shape as that of the first core member 614, and includes asecond core base portion 622, a cylindrical wall 623 provided withsecond positioning convex portion 623 a and a cut out portion 623 b, andsecond claw-shaped magnetic poles 624.

The second core member 615 is arranged on the other side (lower side inFIG. 74) in the axial direction with respect to the first core baseportion 618 such that the second core member 615 is opposed to thesecond core base portion 622. The second core member 615 is providedsuch that the second claw-shaped magnetic poles 624 extend toward oneside in the axial direction and the second claw-shaped magnetic pole 624and the first claw-shaped magnetic poles 621 are adjacent to each otherin the circumferential direction.

As shown in FIGS. 75 and 76, the second positioning convex portion 623 aformed on the cylindrical wall 623 of the second core member 615 has thesame shape as that of the first positioning convex portion 619 a, andthe second positioning convex portion 623 a is formed at a positioncorresponding to a circumferential center of a second claw-shapedmagnetic pole 624 a which is adjacent to the first claw-shaped magneticpole 621 a in the circumferential direction. More specifically, thesecond positioning convex portion 623 a is formed on a circumferentialcenter line L2 of the second claw-shaped magnetic pole 624 a as viewedfrom the axial direction. The cut out portion 623 b is formed at aposition of the cylindrical wall 623 which corresponds to the secondpositioning convex portion 623 a, and inside and outside of thecylindrical wall 623 in the radial direction are brought intocommunication with each other through the cut out portion 623 b.

The cylindrical walls 619 and 623 of the first and second core members614 and 615 are in abutment against each other in the axial direction,and the cylindrical walls 619 and 623 connect outer peripheral edges ofthe first and second core base portions 618 and 622 to each other in theaxial direction. According to this, the cylindrical walls 619 and 623configure an outer peripheral wall of the stator core SC. The outerperipheral wall of the stator core SC formed by the cylindrical walls619 and 623 opens in the radial direction in the cut out portions 619 band 623 b.

As shown in FIGS. 74 to 76, each of the coil portions 616 is formed bywinding a conductor a plurality of times, and the coil portion 616 isplaced between the first core base portion 618 and the second core baseportion 622 in the axial direction. The first claw-shaped magnetic poles621 and the second claw-shaped magnetic poles 624 are alternately placedin the circumferential direction, and the coil portion 616 causes themto function as magnetic poles which are different from each other basedon energization.

One end of the coil portion 616 (first terminal line 616 a) is led out(pulled out) toward an outer periphery of the stator core SC from thecut out portion 619 b of the first core member 614, and the other end ofthe coil portion 616 (second terminal line 616 b) is led out toward theouter periphery of the stator core SC from the cut out portion 623 b ofthe second core member 615.

As shown in FIGS. 73 and 74, the V-phase stator 613 b has substantiallythe same configuration as that of the U-phase stator 613 a. The V-phasestator 613 b is stacked such that angle positions of the first andsecond claw-shaped magnetic poles 621 and 624 are displaced from theU-phase stator 613 a by 60° in electrical angle (5° in mechanical angle)in the clockwise direction. That is, the V-phase stator 613 b is stackedsuch that it is displaced from the U-phase stator 613 a in phase by 60°in electrical angle in the clockwise direction.

The W-phase stator 613 c has substantially the same configuration asthat of the U-phase stator 613 a. The W-phase stator 613 c is stackedsuch that angle positions of the first and second claw-shaped magneticpoles 621 and 624 are displaced from the V-phase stator 613 b by 60° inelectrical angle (5° in mechanical angle) in the clockwise direction.That is, the W-phase stator 613 c is stacked such that it is displacedfrom the V-phase stator 613 b in phase by 60° in electrical angle in theclockwise direction.

If sets of the first and second positioning convex portions 619 a and623 a in the stator cores SC of the respective phases are viewed as onegroup, the stators 613 a, 613 b and 613 c are stacked on one anothersuch that these sets are located substantially at equal intervals fromone another (substantially 120° intervals) in the circumferentialdirection.

As shown in FIG. 72, the stators 613 a, 613 b and 613 c are accommodatedin the cylindrical yoke housing H in a state where the stators arestacked on one another in the axial direction.

Here, as shown in FIG. 73, six positioning recesses 632 (housing-sidepositioning portions) which are recessed in the radial direction areformed in the inner peripheral surface 631 of the yoke housing H. Thepositioning recesses 632 are formed at positions corresponding to thefirst and second positioning convex portions 619 a and 623 a formed onthe stator cores SC of the respective phases. That is, the positioningrecesses 632 are formed two each at three locations of the yoke housingH substantially at equal intervals from one another (substantially 120°intervals) in the circumferential direction.

The positioning recesses 632 straightly extend in the axial directionfrom an axial end surface of the yoke housing H to an axial intermediateportion of the yoke housing H. That is, one axial end of each of thepositioning recesses 632 is an opening end into which the first andsecond positioning convex portions 619 a and 623 a can be inserted fromthe axial direction, and the other axial end of the positioning recess632 is a closed end 632 a which can abut against the first and secondpositioning convex portions 619 a and 623 a in the axial direction.Circumferential widths of the positioning recesses 632 are substantiallyequal to circumferential widths of the first and second positioningconvex portions 619 a and 623 a.

The first and second positioning convex portions 619 a and 623 a arepress fitted into and fixed to the positioning recesses 632 from theaxial direction, and are engaged with both circumferential sides of thepositioning recesses 632 (see FIG. 75). According to this, the stators613 of the respective phases are positioned with respect to the yokehousing H in the circumferential direction.

The first and second positioning convex portions 619 a and 623 a abutagainst the closed ends 632 a of the positioning recesses 632 in theaxial direction. According to this, the stators 613 of the respectivephases are positioned with respect to the yoke housing H in the axialdirection. The closed ends 632 a of the positioning recesses 632 areformed such that their axial positions are different in accordance withdifferences in axial positions of the positioning convex portion 619 aand 623 a.

As shown in FIG. 72, the U-phase rotor 612 a in the rotor 612 includes apair of rotor cores 642 on which claw-shaped magnetic poles 641 arerespectively formed, and a field magnet 643 placed between the rotorcores 642 in the axial direction. The field magnet 643 is magnetized inthe axial direction, and the field magnet 643 causes the claw-shapedmagnetic poles 641 to function as magnetic poles which are alternatelydifferent from each other in the circumferential direction. That is, therotor 612 a is of so-called Lundell type structure. Since the V-phaserotor and the W-phase rotor (not shown) are the same as the U-phaserotor 612 a, description thereof will be omitted.

The V-phase rotor is stacked such that it is displaced from the U-phaserotor 612 a in phase by 60° in electrical angle in the counterclockwisedirection. The W-phase rotor is stacked such that it is displaced fromthe V-phase rotor in phase by 60° in electrical angle in thecounterclockwise direction (i.e., W-phase rotor is displaced fromU-phase rotor 612 a in phase by 120° in electrical angle in thecounterclockwise direction). That is, a phase-deviating direction of thethree-phase rotor in the rotor 612 is opposite from the phase-deviatingdirection (deviation in the clockwise direction) of three-phase in thestator 613.

Next, operations of the tenth embodiment will be described.

If three-phase drive current is supplied to the U-phase, V-phase andW-phase coil portions 616 by a drive circuit (not shown), rotating fieldis generated by the stator 613, and the rotor 612 is rotated and driven.At this time, rotation (speed and direction of rotation) of the rotor612 is detected by a Hall IC (not shown). Based on the detection signal,three-phase drive current is supplied from the drive circuit to the coilportions 616 at optimal timing. According to this, rotating field isexcellently generated, and the rotor 612 is excellently and continuouslyrotated and driven.

Here, in the tenth embodiment, the first and second positioning convexportions 619 a and 623 a of the stator 613 are fastened to thepositioning recesses 632 of the yoke housing H in the circumferentialdirection and the axial direction. According to this, the stator 613 isprecisely assembled with respect to the yoke housing H.

As shown in FIG. 76, when the rotor 612 rotates, for example, magneticfluxes φ flow through the first claw-shaped magnetic poles 621 on theside of their outer peripheries, branch off toward both sides at thecylindrical wall 619 in the circumferential direction, the branchedmagnetic fluxes φ pass through the cylindrical wall 623 of the secondcore member 615, and flow into the second claw-shaped magnetic poles 624on the side of inner peripheries thereof. Here, the first and secondpositioning convex portions 619 a and 623 a are formed on thecircumferential center lines L1 and L2 of the first and secondclaw-shaped magnetic poles 621 and 624. That is, the positioning convexportion 619 a and 623 a are formed at positions where a flow of magneticfluxes φ is less prone to be hindered. As a result, reduction in motoroutput is suppressed.

Next, characteristic advantages of the tenth embodiment will bedescribed below.

(37) The first and second positioning convex portions 619 a and 623 aare respectively formed on the cylindrical walls 619 and 623 of thestator core SC. The first and second positioning convex portions 619 aand 623 a can engage with the positioning recesses 632 in thecircumferential direction. The positioning recesses 632 are provided inthe inner peripheral surface 631 of the yoke housing H. Hence, it ispossible to position the stator 613 in the circumferential direction bya simple configuration.

(38) The first and second positioning convex portions 619 a and 623 aare respectively formed by radially outwardly bending and formingportions of the cylindrical walls 619 and 623. Hence, it is possible toposition the stator 613 in the circumferential direction by a simpleconfiguration, i.e., by bending and forming the positioning convexportion 619 a and 623 a.

(39) The first and second positioning convex portions 619 a and 623 aare respectively formed by cut out portions of the cylindrical walls 619and 623. Terminal lines 616 a and 616 b of the coil portion 616 are ledout from the cut out portions 619 b and 623 b formed by forming thepositioning convex portion 619 a and 623 a. That is, the terminal lines616 a and 616 b of the coil portion 616 are led out from the cut outportions 619 b and 623 b which are formation traces of the positioningconvex portion 619 a and 623 a. Hence, a shape of the stator core SC canbe simplified by the configuration of the tenth embodiment.

(40) The first and second positioning convex portions 619 a and 623 aare engaged with the positioning recesses 632 (closed ends 632 a) of theyoke housing H also in the axial direction. Hence, it is possible toposition the stator 613 in the axial direction by a simpleconfiguration.

(41) The first and second positioning convex portions 619 a and 623 aare formed at positions respectively corresponding to circumferentialcenters of the first and second claw-shaped magnetic poles 621 and 624.According to this configuration, the first and second positioning convexportions 619 a and 623 a are formed at position of the stator core SCdisplaced from a main path of magnetic fluxes. Hence, it is possible torestrain the first and second positioning convex portions 619 a and 623a from hindering a flow of magnetic fluxes.

(42) The stators 613 a, 613 b and 613 c are stacked on one another suchthat the sets of the first and second positioning convex portions 619 aand 623 a (and sets of pairs of the positioning recesses 632) arelocated substantially at equal intervals (substantial 120° intervals)from one another in the circumferential direction. Hence, it is possibleto substantially equalize a stress applied from the stator 613 to theyoke housing H, and it is possible to fix the stator 613 to the yokehousing H in a well balanced manner.

(43) The rotor 612 includes a pair of rotor cores 642 on which theplurality of claw-shaped magnetic poles 641 are respectively formed, andthe field magnet 643 placed between the rotor cores 642 in the axialdirection. The field magnet 643 is magnetized in the axial direction tocause the claw-shaped magnetic poles 641 to function as magnetic poleswhich are alternately different from each other in the circumferentialdirection. The stators 613 and the rotors 612 are arranged in amulti-part manner in the axial direction. According to thisconfiguration, in the motor in which the stators 613 and the rotors 612are arranged in the multi-part manner in the axial direction, it ispossible to position the stators 613 with respect to the yoke housing Hin the circumferential direction by a simple configuration.

(44) The stator 613 includes the U-phase, V-phase and W-phase stators613 a to 613 c which are arranged in a three-part manner in the axialdirection, and the rotor 612 also includes the U-phase, V-phase andW-phase rotors which are arranged in a three-part manner in the axialdirection. The V-phase rotor (second part rotor) is placed such that itis displaced from the U-phase rotor 612 a (first part rotor) in thecounterclockwise direction, and the W-phase rotor (third part rotor) isplaced such that it is displaced from the V-phase rotor in thecounterclockwise direction. The V-phase stator 613 b (second partstator) is placed such that it is displaced from the U-phase stator 613a (first part stator) in the clockwise direction, and the W-phase stator613 c (third part stator) is placed such that it is displaced from theV-phase stator 613 b in the clockwise direction. That is, thephase-deviating direction of the three-phase rotor 612 is opposite fromthe phase-deviating direction of three-phase stator 613. Hence, therotor 612 can excellently rotate.

Eleventh Embodiment

An eleventh embodiment of the motor will be described below inaccordance with FIG. 78. In the eleventh embodiment, a configuration ofa winding lead-out hole which is formed in an outer peripheral portion(cylindrical walls 619 and 623) of a stator core SC and from which anend (lead) of a coil portion 616 is led out is different from that ofthe tenth embodiment. Therefore, the same reference numerals as those ofthe tenth embodiment are allocated to similar configurations, anddetailed description thereof will be omitted. In FIG. 78, a U-phasestator 613 a will be described as an example.

As shown in FIG. 78, cylindrical walls 619 and 623 of first and secondcore members 614 and 615 includes cut out portions 661 a and 661 b whichare formed by cut out portions of ends of the cylindrical walls 619 and623 which abut against each other in the axial direction.Circumferential widths of the cut out portions 661 a and 661 b areequally formed, and the cut out portions 661 a and 661 b are formed atthe same position in the circumferential direction. The cut out portions661 a and 661 b configure one winding lead-out hole 661 which extendsthrough an outer peripheral wall of the stator core SC in the radialdirection. The stator core SC is configured by the cylindrical walls 619and 623. An end (lead 616 c) of the coil portion 616 is inserted intothe winding lead-out hole 661 in the radial direction, and is led outtoward an outer periphery of the stator core SC. It is preferable thatpositions where the cut out portions 661 a and 661 b are formed are setto positions which are circumferentially displaced from portions(portions having narrow circumferential widths) between firstclaw-shaped magnetic poles 621 and between second claw-shaped magneticpoles 624 in the core base portions 618 and 622.

When the stator 613 a of the eleventh embodiment is assembled, the coilportion 616 is first placed on the second core member 615, and the lead616 c of the coil portion 616 is inserted into the cut out portion 661 bof the second core member 615. At this time, a portion of the lead 616 cprojects in the axial direction from an axial end (cut out portion 661b) of the cylindrical wall 623.

Next, the first core member 614 and the second core member 615 areassembled such that they sandwich the coil portion 616. At this time, acircumferential position of the first core member 614 is aligned suchthat the lead 616 c projecting from the cut out portion 661 b of thesecond core member 615 is fitted into the cut out portion 661 a of thefirst core member 614, and the cylindrical wall 619 of the first coremember 614 is made to abut against the cylindrical wall 623 of thesecond core member 615 in the axial direction. According to this, thecircumferential positions of the cut out portions 661 a and 661 bcoincide with each other, and the lead 616 c is led out from the windinglead-out hole 661 formed by the cut out portions 661 a and 661 b.

Next, characteristic advantages of the eleventh embodiment will bedescribed below.

(45) The circumferential positions of the cut out portions 661 a and 661b respectively formed in the first and second core members 614 and 615are made to coincide with each other, thereby configuring the windinglead-out hole 661. The lead 616 c of the coil portion 616 is led outfrom the winding lead-out hole 661. According to this configuration,since the circumferential positions of the cut out portions 661 a and661 b are made to coincide with each other to configure the windinglead-out hole 661. Therefore, it is possible to position the first andsecond core members 614 and 615 in the stator core SC in thecircumferential direction by the simple configuration. In the eleventhembodiment, to enhance positioning precision of the first and secondcore members 614 and 615 in the circumferential direction, it ispreferable that a circumferential widths of the cut out portions 661 aand 661 b are set substantially equal to a diameter of the lead 616 c(coil wire).

(46) The first and second core members 614 and 615 are configured suchthat their cylindrical walls 619 and 623 (outer peripheripheralportions) abut against each other in the axial direction. The windinglead-out hole 661 formed from the cut out portions 661 a and 661 brespectively formed in the cylindrical walls 619 and 623 is configuredsuch that the winding lead-out hole 661 opens in the radial direction ofthe stator core SC. According to this configuration, the lead 616 c ofthe coil portion 616 can be led out radially outward of the stator coreSC.

The eleventh embodiment may be changed as follows.

As shown in FIGS. 79 and 80, a winding fixing member 662 (interposedmember) may be provided between the winding lead-out hole 661 and thelead 616 c. In this another example, the winding fixing member 662 ismade of resin, and formed into a substantially cylindrical shape asshown in FIGS. 80 and 81.

The winding fixing member 662 includes a winding holding portion 663which is tapered (diameter is reduced) toward one side of the windingfixing member 662 in the axial direction. Four slits 663 a are formed inthe winding holding portion 663 at equal intervals from one another (90°intervals) in the circumferential direction of the winding fixing member662. Each of the slits 663 a forms a straight line extending along anaxial direction of the winding fixing member 662. According to this, thewinding holding portion 663 is configured such that it bends in itsradial direction.

Fastening claws 663 b (fastening portions) projecting radially outwardof the winding fixing member 662 are formed on tip ends of the windingholding portions 663. The fastening claws 663 b are fastened to theinner peripheral surfaces of the cylindrical walls 619 and 623.

In this another example, the cut out portions 661 a and 661 b arerecessed into semi-circular shapes, and the winding lead-out hole 661formed from the cut out portions 661 a and 661 b is circular in shape asviewed from the radial direction of the stator core SC. A taperedportion 664 whose diameter is reduced radially inward of the stator coreSC is formed on an inner peripheral surface of the winding lead-out hole661. The tapered portion 664 inclines with respect to a radial direction(inserting direction of lead 616 c) of the stator core SC. The taperedportion 664 abuts against the outer peripheral surface of the windingholding portion 663.

When the stator 613 a of this another example is assembled, first, thefirst and second core members 614 and 615 are assembled to sandwich thecoil portion 616. At this time, the circumferential positions of the cutout portions 661 a and 661 b are made to coincide with each other toform the winding lead-out hole 661, and the lead 616 c of the coilportion 616 is inserted into the winding lead-out hole 661 in the radialdirection.

Thereafter, the lead 616 c which is led out from an outer peripheralwall (cylindrical walls 619 and 623) of the stator core SC toward theouter periphery is inserted into the winding fixing member 662. Then,the winding fixing member 662 is inserted into the winding lead-out hole661 from the outer periphery side. At this time, the winding holdingportion 663 in which the slits 663 a are formed abuts against thetapered portion 664 of the winding lead-out hole 661, and the windingholding portion 663 bends radially inward of the winding lead-out hole661. The fastening claw 663 b of the tip end of the winding holdingportion 663 is fastened to the inner peripheral surfaces of thecylindrical walls 619 and 623 by elastic restoration of the windingholding portion 663. According to this, the winding fixing member 662 isrestrained from coming out from the winding lead-out hole 661. Thewinding holding portion 663 is narrowed radially to the inward side ofthe tapered portion 664 by engagement between the tapered portion 664and the winding holding portions 663, and the lead 616 c is sandwichedby the winding holding portions 663. According to this, a fixed state ofthe lead 616 c is stabilized.

According to this configuration also, the circumferential positions ofthe cut out portions 661 a and 661 b are made to coincide with eachother, and it is possible to configure the winding lead-out hole 661.Therefore, it is possible to position the first and second core members614 and 615 in the stator core SC in the circumferential direction by asimple configuration.

Further, according to this another example, since the winding fixingmember 662 is provide between the winding holding portions 663 and thelead 616 c, it is possible to prevent, by the winding fixing member 662,the lead 616 c from coming into contact directly with the windinglead-out hole 661. As a result, it is possible to restrain the lead 616c from being damaged.

The winding lead-out hole 661 includes the tapered portion 664 whichinclines with respect to the inserting direction (radial direction) ofthe lead 616 c, and the winding fixing member 662 includes the windingholding portions 663 which hold the lead 616 c radially inward(direction intersecting with inserting direction of the lead 616 c atright angles) of the winding fixing member 662 by engagement with thetapered portion 664. According to this configuration, by attaching thewinding fixing member 662, it is possible to easily fix the lead 616 cto the winding lead-out hole 661.

The winding fixing member 662 includes the fastening claws 663 b whichare fastened to the inner peripheral surfaces of the cylindrical walls619 and 623. Hence, it is possible to restrain the winding fixing member662 from coming out from the winding lead-out hole 661.

A configuration such as a shape of the winding fixing member 662 is notlimited to the example shown in FIGS. 79 to 81. As shown in FIGS. 82 and83 for example, the winding fixing member 662 may be divided into twomembers in the radial direction as a divided structure. According tothis configuration, the winding fixing member 662 can be attached to anintermediate portion of the lead 616 c without inserting the end of thelead 616 c into the winding fixing member 662.

Further, in the winding fixing member 662 shown in FIGS. 81 and 82, theslits 663 a and the fastening claws 663 b may be omitted from thewinding holding portion 663.

In this another example, the winding fixing member 662 is attached tothe winding lead-out hole 661 from the outer peripheral side, but theinvention is not especially limited to this configuration. The windingfixing member 662 may be attached to the winding lead-out hole 661 fromthe inner peripheral side.

In the example shown in FIGS. 78 and 79, the stator 613 a is the outerstator provided at its inner periphery with the first and secondclaw-shaped magnetic poles 621 and 624, but the invention is notespecially limited to this configuration. The invention may be appliedto an inner stator provided at its outer periphery with the first andsecond claw-shaped magnetic poles.

The tenth and eleventh embodiments may be changed as follows.

A convex and concave relation between the positioning recess 632 and thepositioning convex portion 619 a and 623 a in the tenth embodiment maybe reversed.

In the example shown in FIG. 77 for example, the cylindrical walls 619and 623 of the first and second core members 614 and 615 respectivelyinclude cut out recesses 651 and 652 (stator-side positioning portions)which are formed by cut out portions of the cylindrical walls 619 and623 from their axial tip end surfaces, and bending these cut outportions radially inward substantially at right angles. The recesses 651and 652 in FIG. 77 are formed at the same positions as those of thepositioning convex portion 619 a and 623 a (cut out portions 619 b and623 b) of the tenth embodiment.

A plurality of housing-side positioning portions 653 projecting radiallyinward are formed on the inner peripheral surface 631 of the yokehousing H, and the housing-side positioning portions 653 are fitted intothe cutout recesses 651 and 652. The housing-side positioning portions653 are fastened to the cut out recesses 651 and 652 in thecircumferential direction and the axial direction. According to this,the first and second core members 614 and 615 are positioned withrespect to the yoke housing H in the circumferential direction and theaxial direction. According to this configuration also, the sameadvantages as those of the tenth embodiment can be obtained.

A configuration such as a shape of the stator core SC formed from theseparate first and second core members 614 and 615 is not limited tothose of the tenth and eleventh embodiments. For example, although thecylindrical walls 619 and 623 are respectively arranged on the first andsecond core members 614 and 615 in the tenth embodiment, the cylindricalwall may be formed only on the first core member 614 or the second coremember 615. The first and second core members 614 and 615 of the tenthembodiment may be configured as an integral stator core. The number ofand shapes of the first and second claw-shaped magnetic poles 621 and624 may appropriately be changed.

Configurations such as formed positions, the number of and shapes of thepositioning convex portions 619 a and 623 a are not limited to those ofthe tenth and eleventh embodiments. For example, the first and secondpositioning convex portions 619 a and 623 a may be formed at positionsdisplaced from the circumferential center lines L1 and L2 of the firstand second claw-shaped magnetic poles 621 and 624. One or three or morepositioning convex portions may be arranged on each of the U-phase,V-phase and W-phase stators 613 a, 613 b and 613 c. The positioningconvex portion 619 a and 623 a may not be formed by the cutting out andbending operations unlike the tenth and eleventh embodiments only if thepositioning convex portions 619 a and 623 a project radially outward.

Although the present invention is applied to the brushless motor Mhaving the three layered rotors 612 and the stators 613 in the tenth andeleventh embodiments, the invention may be applied to a motor havingfour or more layered rotors and stators.

Twelfth Embodiment

A twelfth embodiment of the present invention will be described below.

As shown in FIG. 84, a brushless motor M includes a rotor 722 fixed to arotation shaft 721, and a stator 723 placed on the outer side of therotor 722. The rotation shaft 721 is rotatably supported by a motorhousing (not shown). The stator 723 is fixed to the motor housing (notshown) for example. The stator 723 may be accommodated in a yoke housing(not shown) and the yoke housing may be fixed to the motor housing.

The brushless motor M has such a structure that three motor portions arearranged in an axial direction of the rotation shaft 721. That is, thebrushless motor M includes a U-phase motor portion Mu, a V-phase motorportion Mv and a W-phase motor portion Mw. The U-phase motor portion Muincludes a rotor 722 u and a stator 723 u. Similarly, the V-phase motorportion Mv includes a rotor (not shown) and a stator 723 v, and theW-phase motor portion Mw includes a rotor (not shown) and a stator 723w. Therefore, corresponding to the motor portions Mu, Mv and Mw, therotor 722 includes a U-phase rotor 722 u, a V-phase rotor (not shown)and a W-phase rotor (not shown). Similarly, corresponding to the motorportions Mu, Mv and Mw, the stator 723 includes a U-phase stator 723 u,a V-phase stator 723 v and a W-phase stator 723 w.

As shown in FIG. 84, the U-phase rotor 722 u includes a pair of rotorcores 732 respectively possessed by claw-shaped magnetic poles 731, anda field magnet 733 placed between the rotor cores 732 in the axialdirection. The field magnet 733 is magnetized in the axial direction,thereby causing the claw-shaped magnetic poles 731 to function asmagnetic poles which are alternately different from each other in acircumferential direction of the motor. That is, the U-phase rotor 722 uis of so-called Lundell type structure. Since the V-phase rotor and theW-phase rotor (both not shown) have the same configuration as that ofthe U-phase rotor 722, description thereof will be omitted.

An outline of the three-phase rotor will be described. The V-phase rotoris stacked such that it is displaced from the U-phase rotor 722 u inphase by 60° in electrical angle in the counterclockwise direction. TheW-phase rotor is stacked such that it is displaced from the V-phaserotor in phase by 60° in electrical angle in the counterclockwisedirection (W-phase rotor is displaced from the U-phase rotor 722 u inphase by 120° in electrical angle in the counterclockwise direction).That is, in the rotor 722, a phase-deviating direction of thethree-phase rotor is opposite from a phase-deviating direction(deviation in the clockwise direction) of the three-phase rotor in thestator 723.

Next, the stator 723 will be described. Since the stators 723 u, 723 vand 723 w have the same structures, the U-phase rotor 723 u will bedescribed, and illustration and description of the V-phase stator 723 vand the W-phase stator 723 w will be omitted.

As shown in FIG. 85, the stator 723 u includes a first stator core 741,a second stator core 742 and a coil 743.

The first stator core 741 includes an annular plate-shaped first corebase 751. A cylindrical first core back 752 extending toward the secondstator core 742 in the axial direction is arranged on an outerperipheral end of the first core base 751. A plurality of (four intwelfth embodiment) first claw-shaped magnetic poles 753 are formed onan inner peripheral end of the first core base 751 at equal intervalsfrom one another (90° intervals) in the circumferential direction. Eachof the first claw-shaped magnetic poles 753 includes a first baseportion 754 extending radially inward from an inner peripheral end ofthe first core base 751, and a first magnetic pole portion 755 extendingin the axial direction from an inner end of the first base portion 754.The first magnetic pole portion 755 is formed into a substantiallytrapezoidal plate-shape as viewed from a radial direction of the motor.That is, in the first magnetic pole portion 755, a radial inner sidesurface (inner surface) 755 a and a radial outer side surface (outersurface) 755 b are flat surfaces.

The second stator core 742 is formed in the same way as the first statorcore 741. The second stator core 742 includes an annular plate-shapedsecond core base 761. A cylindrical second core back 762 extendingtoward the first core base 751 in the axial direction is arranged on anouter peripheral end of the second core base 761. A plurality of (fourin twelfth embodiment) second claw-shaped magnetic poles 763 are formedon an inner peripheral end of the second core base 761 at equalintervals from one another (90° intervals) in the circumferentialdirection. Each of the second claw-shaped magnetic poles 763 includes asecond base portion 764 extending radially inward from an innerperipheral end of the second core base 761, and a second magnetic poleportion 765 extending in the axial direction from an inner end of thesecond base portion 764. The second magnetic pole portion 765 is formedinto a substantially trapezoidal plate-shape as viewed from the radialdirection. The inner surface 765 a and an outer surface 765 b of thesecond magnetic pole portion 765 are flat surfaces.

The first stator core 741 and the second stator core 742 are combinedwith each other such that the first core base 751 and the second corebase 761 are opposed to each other in the axial direction, and the firstclaw-shaped magnetic poles 753 and the second claw-shaped magnetic pole763 are adjacent to each other in the circumferential direction. Thefirst core back 752 of the first stator core 741 and the second coreback 762 of the second stator core 742 are in abutment against eachother in the axial direction.

The coil 743 is placed between the first core base 751 and the secondcore base 761 in the axial direction. A wound shape (outward shape) ofthe coil 743 is an annular shape (octagonal annular shape in thedrawings) in accordance with shapes of the first claw-shaped magneticpoles 753 and the second claw-shaped magnetic pole 763. The coil 743 hasa conductor (copper wire for example) which is wound a plurality oftimes in accordance with the wound shape.

As shown in FIG. 86, in the stator 723 u, the first claw-shaped magneticpoles 753 and the second claw-shaped magnetic poles 763 (shown by brokenlines) are alternately placed in the circumferential direction.

In the radial direction, an outer surface 755 b of the first magneticpole portion 755 of the first claw-shaped magnetic pole 753 is a flatsurface. Similarly, in the radial direction, an outer surface 765 b ofthe second magnetic pole portion 765 of the second claw-shaped magneticpole 763 is a flat surface. The coil 743 is formed into a polygonalannular shape (octagonal annular shape) in accordance with the outersurfaces 755 b and 765 b.

Next, operations of the brushless motor M will be described.

As shown in FIG. 86, the coil 743 is formed into the polygonal annularshape (octagonal annular shape) in accordance with the first claw-shapedmagnetic pole 753 of the first stator core 741 and the secondclaw-shaped magnetic pole 763 of the second stator core 742. Therefore,the coil 743 is positioned by the first claw-shaped magnetic pole 753and the second claw-shaped magnetic pole 763 in the circumferentialdirection of the first stator core 741 and the second stator core 742.According to this, movement of the coil 743 in the circumferentialdirection, i.e., a rotating direction of the brushless motor M issuppressed.

For example, the coil formed into an annular shape moves in the rotatingdirection of the brushless motor M. If the coil moves, a stress isapplied to a wire through which drive current is supplied to the coil,and there is fear that a problem such as breaking of wire occurs.

On the other hand, the coil 743 of the twelfth embodiment is positionedby the first claw-shaped magnetic poles 753 and the second claw-shapedmagnetic poles 763 in the circumferential direction of the first statorcore 741. Hence, the movement of the coil 743 in the circumferentialdirection is suppressed, and a stress applied to a wire through whichpower is supplied to the coil 743 can be reduced. Further, in thecircumferential direction of the first stator core 741, the coil 743abuts against the claw-shaped magnetic poles 753 and 763 (magnetic poleportions 755 and 765) at a plurality of locations. Stresses applied tothe coil 743 at individual contact locations becomes small as comparedwith a case where a coil is fixed at one location. Hence, generation ofa problem such as breaking of wire in the coil 743 can be suppressed.

Further, the coil 743 of the twelfth embodiment is formed into theoctagonal annular shape. Therefore, since a loop is formed in the coil743 through a shorter path as compared with an annular coil, a length ofa wound conductor (copper wire) becomes short. Hence, a resistance value(winding resistance) in the coil 743 can be reduced. For example, in thecase of an octagonal annular coil having a diagonal distance which isequal to a diameter of the annular coil, a resistance value of theoctagonal annular coil becomes smaller than a resistance value of anannular coil by about 3%. Since the resistance value of the coil 743 isreduced, an amount of current flowing through the coil 743 is increased,and an amount of magnetic fluxes generated in the stator 723 u isincreased in accordance with the amount of current. As described above,it is possible to enhance characteristics in the brushless motor M.

As shown in FIG. 86, spaces 758 are formed between the coil 743 and thefirst core back 752 of the first stator core 741. Spaces are also formedby the second stator core 742. It is possible to lead out, in the axialdirection, wires through which power is supplied to the coils 743 of themotor portions Mu, My and Mw through the spaces 758.

The first stator core 741 is punched out from a steel plate by metalpunching for example. The first claw-shaped magnetic pole 753 is formedby bending by metal punching. Similarly, the second stator core 742 ispunched out from a steel plate by metal punching for example, and thefirst claw-shaped magnetic pole 753 is formed by bending by metalpunching. In this manner, the stator 723 u (first stator core 741 andsecond stator core 742) can be formed by metal punching. Since thestator 723 u can be formed by metal punching, the number of stepsrequired for a machining operation is reduced, and costs can be reduced.

The twelfth embodiment has the following advantages.

(47) In the first stator core 741, the outer surface 755 b of the firstclaw-shaped magnetic pole 753 (magnetic pole portion 755) is a flatsurface. In the second stator core 742, the outer surface 765 b of thesecond claw-shaped magnetic pole 763 (magnetic pole portion 765) is aflat surface. The first claw-shaped magnetic pole 753 and the secondclaw-shaped magnetic pole 763 can be formed by bending a steel plate bymetal punching. In this manner, the stator 723 u including the firststator core 741 and the second stator core 742 can easily be formed.

(48) The coil 743 placed between the first core base 751 of the firststator core 741 and the second core base 761 of the second stator core742 is formed into a polygonal annular shape (octagonal annular shape)in accordance with the first claw-shaped magnetic poles 753 of the firststator core 741 and the second claw-shaped magnetic poles 763 of thesecond stator core 742. Therefore, the coil 743 is positioned by thefirst claw-shaped magnetic poles 753 and the second claw-shaped magneticpoles 763 in the circumferential direction of the first stator core 741and the second stator core 742. According to this, it is possible tosuppress movement of the coil 743 in the circumferential direction,i.e., the rotating direction of the brushless motor M.

(49) The coil 743 is formed into the polygonal annular shape (octagonalannular shape). Since the loop is formed in the coil 743 through ashorter path as compared with an annular coil, a length of a woundconduct (copper wire) becomes short. Hence, a resistance value (windingresistance) in the coil 743 can be made smaller than that of an annularcoil.

The twelfth embodiment may be carried out in the following manners.

In the twelfth embodiment, a terminal for fixing an end of the coil 743may be placed in the spaces 758 shown in FIG. 86.

A shape of the claw-shaped magnetic pole in the twelfth embodiment mayappropriately be changed as shown in FIGS. 87 to 89.

As shown in FIG. 87 for example, the stator core 770 includes an annularcore base 771, and a cylindrical core back 772 extending in the axialdirection (surface direction in FIG. 87) is arranged on an outerperipheral portion of the core base 771. A plurality of claw-shapedmagnetic poles 773 are formed on an inner periphery of the core base771. Each of the claw-shaped magnetic poles 773 includes a base portion774 extending radially inward from an inner end of the core base 771,and a magnetic pole portion 775 extending in the axial direction(surface direction in FIG. 87) from the base portion 774. An outersurface 775 b of the magnetic pole portion 775 is a flat surface, and aninner surface 775 a of the magnetic pole portion 775 is a curved surfacewhich is curved along the circumferential direction. The claw-shapedmagnetic pole 773 is formed by bending a steel plate by metal punchinglike the twelfth embodiment. The inner surface 775 a can be formedsimultaneously with the bending operation depending upon a shape of apunch used for the metal punching. Since the stator core 770 can beformed by the metal punching in this manner, the number of stepsrequired for a machining operation is reduced, and costs can be reduced.

According to the claw-shaped magnetic pole 773 (magnetic pole portion775) shown in FIG. 87, a thickness of the end 773 a in thecircumferential direction is greater than that of a central portion 773b. According to this, a magnetic flux density in the end 773 a can bemade smaller than that of the central portion 773 b. According to this,it is possible to suppress inconvenience such as magnetic saturation.

As shown in FIG. 88A, a stator core 780 includes an annular core base781, and a cylindrical core back 782 extending in the axial direction(surface direction in FIG. 88A) is arranged on an outer peripheralportion of the core base 781. A plurality of claw-shaped magnetic poles783 are formed on an inner periphery of the core base 781. Each of theclaw-shaped magnetic poles 783 includes a base portion 784 extendingradially inward from an inner end of the core base 781, and a pluralityof magnetic pole pieces 785 extending in the axial direction (surfacedirection in FIG. 88A) from the base portion 784. Each of the magneticpole pieces 785 is formed into a rectangular parallelepiped shape.Therefore, an inner surface 785 a and an outer surface 785B of each ofthe magnetic pole pieces 785 are flat surfaces. As shown in FIG. 88B forexample, the magnetic pole piece 785 is formed by bending thestrip-shaped magnetic pole piece 785 at positions shown by broken lines786 by metal punching for example. If the bending positions shown by thebroken lines 786 is formed into a staircase pattern along thecircumferential direction, gaps (air gaps) between tip ends of theclaw-shaped magnetic poles 731 of the rotor 722 u and the magnetic polepieces 785 can substantially be equalized. By forming the claw-shapedmagnetic poles 783 by the plurality of magnetic pole pieces 785, it ispossible to reduce eddy current.

As shown in FIG. 89, a stator core 790 includes an annular core base791, and a cylindrical core back 792 extending in the axial direction(surface direction in FIG. 89) is arranged on an outer peripheralportion of the core base 791. A plurality of claw-shaped magnetic poles793 are formed on an inner periphery of the core base 791. Each of theclaw-shaped magnetic poles 793 includes a base portion 794 extendingradially inward from an inner end of the core base 791, and a pluralityof magnetic pole pieces 795 extending in the axial direction (surfacedirection in FIG. 89) from the base portion 794. Each of the magneticpole pieces 795 is formed into a rectangular parallelepiped shape.Therefore, an inner surface 795 a and an outer surface 795 b of themagnetic pole piece 795 are flat surfaces. For example, the bendingposition of the magnetic pole piece 795 is set along a circumferentialdirection of the stator core 790. Each of the magnetic pole pieces 795is formed such that its outer surface 795 b faces the radial direction.According to this, when the stator is configured, the magnetic polepiece 795 is placed substantially cylindrically. By setting the bendingdirection of the magnetic pole piece 795 as described above, the air gapcan be equalized. Like the stator core 780 shown in FIG. 88A, it ispossible to reduce eddy current by configuring the claw-shaped magneticpoles 793 in the stator core 790 by the plurality of magnetic polepieces 795.

In the stator (stator core) of the twelfth embodiment, an annular coilmay be used.

1. A rotor comprising: first to fourth four rotor cores stacked on oneanother in order in an axial direction of the rotor, the first to fourthrotor cores respectively including a same number of first to fourthrotor-side claw-shaped magnetic poles, the first to fourth rotor-sideclaw-shaped magnetic poles are respectively extending from and formed onthe first to fourth rotor cores at equal angle intervals; and aplurality of field magnets respectively interposed between the first tofourth rotor cores, wherein a tip end surface of the first rotor-sideclaw-shaped magnetic pole and a tip end surface of the third rotor-sideclaw-shaped magnetic pole abut against or are closely opposed to eachother in the axial direction, a tip end surface of the second rotor-sideclaw-shaped magnetic pole and a tip end surface of the fourth rotor-sideclaw-shaped magnetic pole abut against or are closely opposed to eachother in the axial direction, the plurality of field magnets aremagnetized in the axial direction such that the field magnets cause thefirst and third rotor-side claw-shaped magnetic poles to function asfirst magnetic poles, and cause the second and fourth rotor-sideclaw-shaped magnetic poles to function as second magnetic poles.
 2. Therotor according to claim 1, wherein the plurality of field magnetsinclude a field magnet interposed between the first rotor core and thesecond rotor core, a field magnet interposed between the second rotorcore and the third rotor core, and a field magnet interposed between thethird rotor core and the fourth rotor core, a portion of the fieldmagnet interposed between the first rotor core and the second rotor corecloser to the first rotor core in the axial direction is magnetized intofirst magnetic pole, and a portion thereof closer to the second rotorcore in the axial direction is magnetized into second magnetic pole, aportion of the field magnet interposed between the second rotor core andthe third rotor core closer to the second rotor core in the axialdirection is magnetized into the second magnetic pole, and a portionthereof closer to the third rotor core in the axial direction ismagnetized into the first magnetic pole, and a portion of the fieldmagnet interposed between the third rotor core and the fourth rotor corecloser to the third rotor core in the axial direction is magnetized intothe first magnetic pole, and a portion thereof closer to the fourthrotor core in the axial direction is magnetized into the second magneticpole.
 3. The rotor according to claim 1, wherein the plurality of fieldmagnets include a field magnet interposed between the first rotor coreand the second rotor core, a field magnet interposed between the secondrotor core and the third rotor core, and a field magnet interposedbetween the third rotor core and the fourth rotor core, and lengths ofthe plurality of field magnets in the axial direction are equal to oneanother.
 4. The rotor according to claim 3, wherein magnetic forces ofthe plurality of field magnets having the same lengths in the axialdirection are equal to one another.
 5. A stator comprising: first tofourth four stator cores stacked on one another in order in an axialdirection of the stator, the first to fourth stator cores respectivelyincluding same number of first to fourth stator-side claw-shapedmagnetic poles, the first to fourth stator-side claw-shaped magneticpoles are respectively extending from and formed on the first to fourthstator cores at equal angle intervals; and a plurality of annularwindings respectively interposed between the first to fourth statorcores, wherein a tip end surface of the first stator-side claw-shapedmagnetic pole and a tip end surface of the third stator-side claw-shapedmagnetic pole abut against or are closely opposed to each other in theaxial direction, a tip end surface of the second stator-side claw-shapedmagnetic pole and a tip end surface of the fourth stator-sideclaw-shaped magnetic pole abut against or are closely opposed to eachother in the axial direction, and directions of AC current flowingthrough the plurality of annular windings are different from one anothersuch that a variation cycle of magnetic fluxes from the first and thirdstator-side claw-shaped magnetic poles and a variation cycle of magneticfluxes from the second and fourth stator-side claw-shaped magnetic polesare deviated from each other in phase by 180°.
 6. The stator accordingto claim 5, wherein the plurality of annular windings include an annularwinding interposed between the first stator core and the second statorcore, an annular winding interposed between the second stator core andthe third stator core, and an annular winding interposed between thethird stator core and the fourth stator core, the annular windinginterposed between the first stator core and the second stator core iswound normally, the annular winding interposed between the second statorcore and the third stator core is wound reversely, the annular windinginterposed between the third stator core and the fourth stator core iswound normally, and single-phase current flows through each of theplurality of annular windings.
 7. The stator according to claim 5,wherein the plurality of annular windings include an annular windinginterposed between the first stator core and the second stator core, anannular winding interposed between the second stator core and the thirdstator core, and an annular winding interposed between the third statorcore and the fourth stator core, and coil lengths of the plurality ofannular windings are equal to one another.
 8. The stator according toclaim 7, wherein winding numbers of the plurality of annular windingshaving the same coil lengths are equal to one another.
 9. A motorcomprising: a shaft extending along an axial direction of the motor; arotor including a first rotor core having a plurality of first rotorclaw-shaped magnetic poles arranged at equal intervals from one anotherin a circumferential direction of the motor, a second rotor core havinga plurality of second rotor claw-shaped magnetic poles arranged at equalintervals from one another in the circumferential direction, and anannular field magnet placed between the first and second rotor cores andmagnetized in the axial direction, the first and second rotorclaw-shaped magnetic poles being alternately placed in thecircumferential direction, and the field magnet is configured so as tocause the first and second rotor claw-shaped magnetic poles to functionas magnetic poles which are different from each other; and a statorincluding a first stator core having a plurality of first statorclaw-shaped magnetic poles arranged at equal intervals from one anotherin the circumferential direction, a second stator core having aplurality of second stator claw-shaped magnetic poles arranged at equalintervals from one another in the circumferential direction, and a coilportion placed between the first and second stator cores and wound inthe circumferential direction, the first and second stator claw-shapedmagnetic poles being placed alternately in the circumferential directionand being opposed to the first and second rotor claw-shaped magneticpoles, and the coil portion is configured so as to cause the first andsecond stator claw-shaped magnetic poles to function as magnetic poleswhich are different from each other based on energization to the coilportion, and cause polarities of the first and second stator claw-shapedmagnetic poles to switch to each other, wherein the shaft extendsthrough one of the rotor and the stator, and wherein the first andsecond rotor and the first and second stator have an equal number ofclaw-shaped magnetic poles.
 10. The motor according to claim 9, furthercomprising a non-magnetic portion arranged between the field magnet andthe first and second rotor claw-shaped magnetic poles, wherein thenon-magnetic portion positions the field magnet in a radial direction ofthe motor.
 11. The motor according to claim 9, further comprisingauxiliary magnets respectively attached to an upper surface and a lowersurface of the rotor.
 12. The motor according to claim 9, wherein eachof the plurality of first rotor claw-shaped magnetic poles includes anextending portion extending in a radial direction of the motor, and aclaw extending in the axial direction from a radial outer end of theextending portion, each of the second rotor claw-shaped magnetic polesincludes an extending portion extending in the radial direction, and aclaw extending in the axial direction from a radial outer end of theextending portion, the field magnet is placed between the extendingportion of the first claw-shaped magnetic pole and the extending portionof the second claw-shaped magnetic pole, a first axial end surface ofthe field magnet is exposed from a gap between the mutually adjacentextending portions of the first rotor claw-shaped magnetic poles, and asecond axial end surface of the field magnet is exposed from a gapbetween the mutually adjacent extending portions of the second rotorclaw-shaped magnetic poles.
 13. The motor according to claim 9, whereinthe rotor is one of a plurality of single rotors stacked along the axialdirection, the first rotor core includes a first core base and theplurality of first rotor claw-shaped magnetic poles, the plurality offirst rotor claw-shaped magnetic poles are configured separately fromthe first core base, and are fixed to the first core base, the secondrotor core includes a second core base and the plurality of second rotorclaw-shaped magnetic poles, the plurality of second rotor claw-shapedmagnetic poles are configured separately from the second core base, andare fixed to the second core base, at least the first rotor claw-shapedmagnetic poles of the single rotors which are adjacent to each other inthe axial direction are integrally connected to each other, and at leastthe second rotor claw-shaped magnetic poles of the single rotors whichare adjacent to each other in the axial direction are integrallyconnected to each other.
 14. The motor according to claim 9, wherein thestator includes a core back portion which connects the first stator coreand the second stator core to each other and which configures an outerperiphery of the stator, the stator core comprises an integrally formedpunched material including the first stator core, the plurality of firststator claw-shaped magnetic poles, the second stator core, the pluralityof second stator magnetic poles and the core back portion, and thestator core is formed by forming the punched material into an annularshape and by connecting both ends of the punched material to each other.15. The motor according to claim 9, further comprising a cylindricalhousing, which accommodates the first and second stator cores, wherein ahousing-side positioning portion is arranged on an inner peripheralsurface of the housing, the first stator core and the second stator corerespectively include outer peripheral portions, the outer peripheralportions connect the first stator core and the second stator core toeach other, which are opposed in the axial direction, the plurality offirst stator claw-shaped magnetic poles and the plurality of secondstator claw-shaped magnetic poles are respectively arranged on an innerperipheral portion of the first stator core and an inner peripheralportion of the second stator core, and stator-side positioning portionswhich engage with the housing-side positioning portion in thecircumferential direction are respectively formed on an outer peripheralportion of the first stator core and an outer peripheral portion of thesecond stator core.
 16. The motor according to claim 9, wherein cut outportions are respectively formed in the first stator core and the secondstator core, a winding lead-out hole is configured by bringingcircumferential positions of the cut out portions into line with eachother, and an end of the coil portion is pulled out from the windinglead-out hole.
 17. The motor according to claim 9, wherein an outersurface of each of the plurality of first stator claw-shaped magneticpoles is a flat surface, and an outer surface of each of the pluralityof second stator claw-shaped magnetic poles is a flat surface.